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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1995 Linus Torvalds
4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 */
7#include <linux/sched.h> /* test_thread_flag(), ... */
8#include <linux/sched/task_stack.h> /* task_stack_*(), ... */
9#include <linux/kdebug.h> /* oops_begin/end, ... */
10#include <linux/extable.h> /* search_exception_tables */
11#include <linux/memblock.h> /* max_low_pfn */
12#include <linux/kfence.h> /* kfence_handle_page_fault */
13#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
14#include <linux/mmiotrace.h> /* kmmio_handler, ... */
15#include <linux/perf_event.h> /* perf_sw_event */
16#include <linux/hugetlb.h> /* hstate_index_to_shift */
17#include <linux/prefetch.h> /* prefetchw */
18#include <linux/context_tracking.h> /* exception_enter(), ... */
19#include <linux/uaccess.h> /* faulthandler_disabled() */
20#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
21#include <linux/mm_types.h>
22
23#include <asm/cpufeature.h> /* boot_cpu_has, ... */
24#include <asm/traps.h> /* dotraplinkage, ... */
25#include <asm/fixmap.h> /* VSYSCALL_ADDR */
26#include <asm/vsyscall.h> /* emulate_vsyscall */
27#include <asm/vm86.h> /* struct vm86 */
28#include <asm/mmu_context.h> /* vma_pkey() */
29#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
30#include <asm/desc.h> /* store_idt(), ... */
31#include <asm/cpu_entry_area.h> /* exception stack */
32#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
33#include <asm/kvm_para.h> /* kvm_handle_async_pf */
34#include <asm/vdso.h> /* fixup_vdso_exception() */
35#include <asm/irq_stack.h>
36
37#define CREATE_TRACE_POINTS
38#include <asm/trace/exceptions.h>
39
40/*
41 * Returns 0 if mmiotrace is disabled, or if the fault is not
42 * handled by mmiotrace:
43 */
44static nokprobe_inline int
45kmmio_fault(struct pt_regs *regs, unsigned long addr)
46{
47 if (unlikely(is_kmmio_active()))
48 if (kmmio_handler(regs, addr) == 1)
49 return -1;
50 return 0;
51}
52
53/*
54 * Prefetch quirks:
55 *
56 * 32-bit mode:
57 *
58 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
59 * Check that here and ignore it. This is AMD erratum #91.
60 *
61 * 64-bit mode:
62 *
63 * Sometimes the CPU reports invalid exceptions on prefetch.
64 * Check that here and ignore it.
65 *
66 * Opcode checker based on code by Richard Brunner.
67 */
68static inline int
69check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
70 unsigned char opcode, int *prefetch)
71{
72 unsigned char instr_hi = opcode & 0xf0;
73 unsigned char instr_lo = opcode & 0x0f;
74
75 switch (instr_hi) {
76 case 0x20:
77 case 0x30:
78 /*
79 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
80 * In X86_64 long mode, the CPU will signal invalid
81 * opcode if some of these prefixes are present so
82 * X86_64 will never get here anyway
83 */
84 return ((instr_lo & 7) == 0x6);
85#ifdef CONFIG_X86_64
86 case 0x40:
87 /*
88 * In 64-bit mode 0x40..0x4F are valid REX prefixes
89 */
90 return (!user_mode(regs) || user_64bit_mode(regs));
91#endif
92 case 0x60:
93 /* 0x64 thru 0x67 are valid prefixes in all modes. */
94 return (instr_lo & 0xC) == 0x4;
95 case 0xF0:
96 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
97 return !instr_lo || (instr_lo>>1) == 1;
98 case 0x00:
99 /* Prefetch instruction is 0x0F0D or 0x0F18 */
100 if (get_kernel_nofault(opcode, instr))
101 return 0;
102
103 *prefetch = (instr_lo == 0xF) &&
104 (opcode == 0x0D || opcode == 0x18);
105 return 0;
106 default:
107 return 0;
108 }
109}
110
111static bool is_amd_k8_pre_npt(void)
112{
113 struct cpuinfo_x86 *c = &boot_cpu_data;
114
115 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
116 c->x86_vendor == X86_VENDOR_AMD &&
117 c->x86 == 0xf && c->x86_model < 0x40);
118}
119
120static int
121is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
122{
123 unsigned char *max_instr;
124 unsigned char *instr;
125 int prefetch = 0;
126
127 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
128 if (!is_amd_k8_pre_npt())
129 return 0;
130
131 /*
132 * If it was a exec (instruction fetch) fault on NX page, then
133 * do not ignore the fault:
134 */
135 if (error_code & X86_PF_INSTR)
136 return 0;
137
138 instr = (void *)convert_ip_to_linear(current, regs);
139 max_instr = instr + 15;
140
141 /*
142 * This code has historically always bailed out if IP points to a
143 * not-present page (e.g. due to a race). No one has ever
144 * complained about this.
145 */
146 pagefault_disable();
147
148 while (instr < max_instr) {
149 unsigned char opcode;
150
151 if (user_mode(regs)) {
152 if (get_user(opcode, (unsigned char __user *) instr))
153 break;
154 } else {
155 if (get_kernel_nofault(opcode, instr))
156 break;
157 }
158
159 instr++;
160
161 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
162 break;
163 }
164
165 pagefault_enable();
166 return prefetch;
167}
168
169DEFINE_SPINLOCK(pgd_lock);
170LIST_HEAD(pgd_list);
171
172#ifdef CONFIG_X86_32
173static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
174{
175 unsigned index = pgd_index(address);
176 pgd_t *pgd_k;
177 p4d_t *p4d, *p4d_k;
178 pud_t *pud, *pud_k;
179 pmd_t *pmd, *pmd_k;
180
181 pgd += index;
182 pgd_k = init_mm.pgd + index;
183
184 if (!pgd_present(*pgd_k))
185 return NULL;
186
187 /*
188 * set_pgd(pgd, *pgd_k); here would be useless on PAE
189 * and redundant with the set_pmd() on non-PAE. As would
190 * set_p4d/set_pud.
191 */
192 p4d = p4d_offset(pgd, address);
193 p4d_k = p4d_offset(pgd_k, address);
194 if (!p4d_present(*p4d_k))
195 return NULL;
196
197 pud = pud_offset(p4d, address);
198 pud_k = pud_offset(p4d_k, address);
199 if (!pud_present(*pud_k))
200 return NULL;
201
202 pmd = pmd_offset(pud, address);
203 pmd_k = pmd_offset(pud_k, address);
204
205 if (pmd_present(*pmd) != pmd_present(*pmd_k))
206 set_pmd(pmd, *pmd_k);
207
208 if (!pmd_present(*pmd_k))
209 return NULL;
210 else
211 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
212
213 return pmd_k;
214}
215
216/*
217 * Handle a fault on the vmalloc or module mapping area
218 *
219 * This is needed because there is a race condition between the time
220 * when the vmalloc mapping code updates the PMD to the point in time
221 * where it synchronizes this update with the other page-tables in the
222 * system.
223 *
224 * In this race window another thread/CPU can map an area on the same
225 * PMD, finds it already present and does not synchronize it with the
226 * rest of the system yet. As a result v[mz]alloc might return areas
227 * which are not mapped in every page-table in the system, causing an
228 * unhandled page-fault when they are accessed.
229 */
230static noinline int vmalloc_fault(unsigned long address)
231{
232 unsigned long pgd_paddr;
233 pmd_t *pmd_k;
234 pte_t *pte_k;
235
236 /* Make sure we are in vmalloc area: */
237 if (!(address >= VMALLOC_START && address < VMALLOC_END))
238 return -1;
239
240 /*
241 * Synchronize this task's top level page-table
242 * with the 'reference' page table.
243 *
244 * Do _not_ use "current" here. We might be inside
245 * an interrupt in the middle of a task switch..
246 */
247 pgd_paddr = read_cr3_pa();
248 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
249 if (!pmd_k)
250 return -1;
251
252 if (pmd_large(*pmd_k))
253 return 0;
254
255 pte_k = pte_offset_kernel(pmd_k, address);
256 if (!pte_present(*pte_k))
257 return -1;
258
259 return 0;
260}
261NOKPROBE_SYMBOL(vmalloc_fault);
262
263static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end)
264{
265 unsigned long addr;
266
267 for (addr = start & PMD_MASK;
268 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
269 addr += PMD_SIZE) {
270 struct page *page;
271
272 spin_lock(&pgd_lock);
273 list_for_each_entry(page, &pgd_list, lru) {
274 spinlock_t *pgt_lock;
275
276 /* the pgt_lock only for Xen */
277 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
278
279 spin_lock(pgt_lock);
280 vmalloc_sync_one(page_address(page), addr);
281 spin_unlock(pgt_lock);
282 }
283 spin_unlock(&pgd_lock);
284 }
285}
286
287void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
288{
289 __arch_sync_kernel_mappings(start, end);
290#ifdef CONFIG_KMSAN
291 /*
292 * KMSAN maintains two additional metadata page mappings for the
293 * [VMALLOC_START, VMALLOC_END) range. These mappings start at
294 * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and
295 * have to be synced together with the vmalloc memory mapping.
296 */
297 if (start >= VMALLOC_START && end < VMALLOC_END) {
298 __arch_sync_kernel_mappings(
299 start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START,
300 end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START);
301 __arch_sync_kernel_mappings(
302 start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START,
303 end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START);
304 }
305#endif
306}
307
308static bool low_pfn(unsigned long pfn)
309{
310 return pfn < max_low_pfn;
311}
312
313static void dump_pagetable(unsigned long address)
314{
315 pgd_t *base = __va(read_cr3_pa());
316 pgd_t *pgd = &base[pgd_index(address)];
317 p4d_t *p4d;
318 pud_t *pud;
319 pmd_t *pmd;
320 pte_t *pte;
321
322#ifdef CONFIG_X86_PAE
323 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
324 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
325 goto out;
326#define pr_pde pr_cont
327#else
328#define pr_pde pr_info
329#endif
330 p4d = p4d_offset(pgd, address);
331 pud = pud_offset(p4d, address);
332 pmd = pmd_offset(pud, address);
333 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
334#undef pr_pde
335
336 /*
337 * We must not directly access the pte in the highpte
338 * case if the page table is located in highmem.
339 * And let's rather not kmap-atomic the pte, just in case
340 * it's allocated already:
341 */
342 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
343 goto out;
344
345 pte = pte_offset_kernel(pmd, address);
346 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
347out:
348 pr_cont("\n");
349}
350
351#else /* CONFIG_X86_64: */
352
353#ifdef CONFIG_CPU_SUP_AMD
354static const char errata93_warning[] =
355KERN_ERR
356"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
357"******* Working around it, but it may cause SEGVs or burn power.\n"
358"******* Please consider a BIOS update.\n"
359"******* Disabling USB legacy in the BIOS may also help.\n";
360#endif
361
362static int bad_address(void *p)
363{
364 unsigned long dummy;
365
366 return get_kernel_nofault(dummy, (unsigned long *)p);
367}
368
369static void dump_pagetable(unsigned long address)
370{
371 pgd_t *base = __va(read_cr3_pa());
372 pgd_t *pgd = base + pgd_index(address);
373 p4d_t *p4d;
374 pud_t *pud;
375 pmd_t *pmd;
376 pte_t *pte;
377
378 if (bad_address(pgd))
379 goto bad;
380
381 pr_info("PGD %lx ", pgd_val(*pgd));
382
383 if (!pgd_present(*pgd))
384 goto out;
385
386 p4d = p4d_offset(pgd, address);
387 if (bad_address(p4d))
388 goto bad;
389
390 pr_cont("P4D %lx ", p4d_val(*p4d));
391 if (!p4d_present(*p4d) || p4d_large(*p4d))
392 goto out;
393
394 pud = pud_offset(p4d, address);
395 if (bad_address(pud))
396 goto bad;
397
398 pr_cont("PUD %lx ", pud_val(*pud));
399 if (!pud_present(*pud) || pud_large(*pud))
400 goto out;
401
402 pmd = pmd_offset(pud, address);
403 if (bad_address(pmd))
404 goto bad;
405
406 pr_cont("PMD %lx ", pmd_val(*pmd));
407 if (!pmd_present(*pmd) || pmd_large(*pmd))
408 goto out;
409
410 pte = pte_offset_kernel(pmd, address);
411 if (bad_address(pte))
412 goto bad;
413
414 pr_cont("PTE %lx", pte_val(*pte));
415out:
416 pr_cont("\n");
417 return;
418bad:
419 pr_info("BAD\n");
420}
421
422#endif /* CONFIG_X86_64 */
423
424/*
425 * Workaround for K8 erratum #93 & buggy BIOS.
426 *
427 * BIOS SMM functions are required to use a specific workaround
428 * to avoid corruption of the 64bit RIP register on C stepping K8.
429 *
430 * A lot of BIOS that didn't get tested properly miss this.
431 *
432 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
433 * Try to work around it here.
434 *
435 * Note we only handle faults in kernel here.
436 * Does nothing on 32-bit.
437 */
438static int is_errata93(struct pt_regs *regs, unsigned long address)
439{
440#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
441 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
442 || boot_cpu_data.x86 != 0xf)
443 return 0;
444
445 if (user_mode(regs))
446 return 0;
447
448 if (address != regs->ip)
449 return 0;
450
451 if ((address >> 32) != 0)
452 return 0;
453
454 address |= 0xffffffffUL << 32;
455 if ((address >= (u64)_stext && address <= (u64)_etext) ||
456 (address >= MODULES_VADDR && address <= MODULES_END)) {
457 printk_once(errata93_warning);
458 regs->ip = address;
459 return 1;
460 }
461#endif
462 return 0;
463}
464
465/*
466 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
467 * to illegal addresses >4GB.
468 *
469 * We catch this in the page fault handler because these addresses
470 * are not reachable. Just detect this case and return. Any code
471 * segment in LDT is compatibility mode.
472 */
473static int is_errata100(struct pt_regs *regs, unsigned long address)
474{
475#ifdef CONFIG_X86_64
476 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
477 return 1;
478#endif
479 return 0;
480}
481
482/* Pentium F0 0F C7 C8 bug workaround: */
483static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
484 unsigned long address)
485{
486#ifdef CONFIG_X86_F00F_BUG
487 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
488 idt_is_f00f_address(address)) {
489 handle_invalid_op(regs);
490 return 1;
491 }
492#endif
493 return 0;
494}
495
496static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
497{
498 u32 offset = (index >> 3) * sizeof(struct desc_struct);
499 unsigned long addr;
500 struct ldttss_desc desc;
501
502 if (index == 0) {
503 pr_alert("%s: NULL\n", name);
504 return;
505 }
506
507 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
508 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
509 return;
510 }
511
512 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
513 sizeof(struct ldttss_desc))) {
514 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
515 name, index);
516 return;
517 }
518
519 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
520#ifdef CONFIG_X86_64
521 addr |= ((u64)desc.base3 << 32);
522#endif
523 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
524 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
525}
526
527static void
528show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
529{
530 if (!oops_may_print())
531 return;
532
533 if (error_code & X86_PF_INSTR) {
534 unsigned int level;
535 pgd_t *pgd;
536 pte_t *pte;
537
538 pgd = __va(read_cr3_pa());
539 pgd += pgd_index(address);
540
541 pte = lookup_address_in_pgd(pgd, address, &level);
542
543 if (pte && pte_present(*pte) && !pte_exec(*pte))
544 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
545 from_kuid(&init_user_ns, current_uid()));
546 if (pte && pte_present(*pte) && pte_exec(*pte) &&
547 (pgd_flags(*pgd) & _PAGE_USER) &&
548 (__read_cr4() & X86_CR4_SMEP))
549 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
550 from_kuid(&init_user_ns, current_uid()));
551 }
552
553 if (address < PAGE_SIZE && !user_mode(regs))
554 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
555 (void *)address);
556 else
557 pr_alert("BUG: unable to handle page fault for address: %px\n",
558 (void *)address);
559
560 pr_alert("#PF: %s %s in %s mode\n",
561 (error_code & X86_PF_USER) ? "user" : "supervisor",
562 (error_code & X86_PF_INSTR) ? "instruction fetch" :
563 (error_code & X86_PF_WRITE) ? "write access" :
564 "read access",
565 user_mode(regs) ? "user" : "kernel");
566 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
567 !(error_code & X86_PF_PROT) ? "not-present page" :
568 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
569 (error_code & X86_PF_PK) ? "protection keys violation" :
570 "permissions violation");
571
572 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
573 struct desc_ptr idt, gdt;
574 u16 ldtr, tr;
575
576 /*
577 * This can happen for quite a few reasons. The more obvious
578 * ones are faults accessing the GDT, or LDT. Perhaps
579 * surprisingly, if the CPU tries to deliver a benign or
580 * contributory exception from user code and gets a page fault
581 * during delivery, the page fault can be delivered as though
582 * it originated directly from user code. This could happen
583 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
584 * kernel or IST stack.
585 */
586 store_idt(&idt);
587
588 /* Usable even on Xen PV -- it's just slow. */
589 native_store_gdt(&gdt);
590
591 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
592 idt.address, idt.size, gdt.address, gdt.size);
593
594 store_ldt(ldtr);
595 show_ldttss(&gdt, "LDTR", ldtr);
596
597 store_tr(tr);
598 show_ldttss(&gdt, "TR", tr);
599 }
600
601 dump_pagetable(address);
602}
603
604static noinline void
605pgtable_bad(struct pt_regs *regs, unsigned long error_code,
606 unsigned long address)
607{
608 struct task_struct *tsk;
609 unsigned long flags;
610 int sig;
611
612 flags = oops_begin();
613 tsk = current;
614 sig = SIGKILL;
615
616 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
617 tsk->comm, address);
618 dump_pagetable(address);
619
620 if (__die("Bad pagetable", regs, error_code))
621 sig = 0;
622
623 oops_end(flags, regs, sig);
624}
625
626static void sanitize_error_code(unsigned long address,
627 unsigned long *error_code)
628{
629 /*
630 * To avoid leaking information about the kernel page
631 * table layout, pretend that user-mode accesses to
632 * kernel addresses are always protection faults.
633 *
634 * NB: This means that failed vsyscalls with vsyscall=none
635 * will have the PROT bit. This doesn't leak any
636 * information and does not appear to cause any problems.
637 */
638 if (address >= TASK_SIZE_MAX)
639 *error_code |= X86_PF_PROT;
640}
641
642static void set_signal_archinfo(unsigned long address,
643 unsigned long error_code)
644{
645 struct task_struct *tsk = current;
646
647 tsk->thread.trap_nr = X86_TRAP_PF;
648 tsk->thread.error_code = error_code | X86_PF_USER;
649 tsk->thread.cr2 = address;
650}
651
652static noinline void
653page_fault_oops(struct pt_regs *regs, unsigned long error_code,
654 unsigned long address)
655{
656#ifdef CONFIG_VMAP_STACK
657 struct stack_info info;
658#endif
659 unsigned long flags;
660 int sig;
661
662 if (user_mode(regs)) {
663 /*
664 * Implicit kernel access from user mode? Skip the stack
665 * overflow and EFI special cases.
666 */
667 goto oops;
668 }
669
670#ifdef CONFIG_VMAP_STACK
671 /*
672 * Stack overflow? During boot, we can fault near the initial
673 * stack in the direct map, but that's not an overflow -- check
674 * that we're in vmalloc space to avoid this.
675 */
676 if (is_vmalloc_addr((void *)address) &&
677 get_stack_guard_info((void *)address, &info)) {
678 /*
679 * We're likely to be running with very little stack space
680 * left. It's plausible that we'd hit this condition but
681 * double-fault even before we get this far, in which case
682 * we're fine: the double-fault handler will deal with it.
683 *
684 * We don't want to make it all the way into the oops code
685 * and then double-fault, though, because we're likely to
686 * break the console driver and lose most of the stack dump.
687 */
688 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
689 handle_stack_overflow,
690 ASM_CALL_ARG3,
691 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
692
693 unreachable();
694 }
695#endif
696
697 /*
698 * Buggy firmware could access regions which might page fault. If
699 * this happens, EFI has a special OOPS path that will try to
700 * avoid hanging the system.
701 */
702 if (IS_ENABLED(CONFIG_EFI))
703 efi_crash_gracefully_on_page_fault(address);
704
705 /* Only not-present faults should be handled by KFENCE. */
706 if (!(error_code & X86_PF_PROT) &&
707 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
708 return;
709
710oops:
711 /*
712 * Oops. The kernel tried to access some bad page. We'll have to
713 * terminate things with extreme prejudice:
714 */
715 flags = oops_begin();
716
717 show_fault_oops(regs, error_code, address);
718
719 if (task_stack_end_corrupted(current))
720 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
721
722 sig = SIGKILL;
723 if (__die("Oops", regs, error_code))
724 sig = 0;
725
726 /* Executive summary in case the body of the oops scrolled away */
727 printk(KERN_DEFAULT "CR2: %016lx\n", address);
728
729 oops_end(flags, regs, sig);
730}
731
732static noinline void
733kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
734 unsigned long address, int signal, int si_code,
735 u32 pkey)
736{
737 WARN_ON_ONCE(user_mode(regs));
738
739 /* Are we prepared to handle this kernel fault? */
740 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
741 /*
742 * Any interrupt that takes a fault gets the fixup. This makes
743 * the below recursive fault logic only apply to a faults from
744 * task context.
745 */
746 if (in_interrupt())
747 return;
748
749 /*
750 * Per the above we're !in_interrupt(), aka. task context.
751 *
752 * In this case we need to make sure we're not recursively
753 * faulting through the emulate_vsyscall() logic.
754 */
755 if (current->thread.sig_on_uaccess_err && signal) {
756 sanitize_error_code(address, &error_code);
757
758 set_signal_archinfo(address, error_code);
759
760 if (si_code == SEGV_PKUERR) {
761 force_sig_pkuerr((void __user *)address, pkey);
762 } else {
763 /* XXX: hwpoison faults will set the wrong code. */
764 force_sig_fault(signal, si_code, (void __user *)address);
765 }
766 }
767
768 /*
769 * Barring that, we can do the fixup and be happy.
770 */
771 return;
772 }
773
774 /*
775 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
776 * instruction.
777 */
778 if (is_prefetch(regs, error_code, address))
779 return;
780
781 page_fault_oops(regs, error_code, address);
782}
783
784/*
785 * Print out info about fatal segfaults, if the show_unhandled_signals
786 * sysctl is set:
787 */
788static inline void
789show_signal_msg(struct pt_regs *regs, unsigned long error_code,
790 unsigned long address, struct task_struct *tsk)
791{
792 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
793 /* This is a racy snapshot, but it's better than nothing. */
794 int cpu = raw_smp_processor_id();
795
796 if (!unhandled_signal(tsk, SIGSEGV))
797 return;
798
799 if (!printk_ratelimit())
800 return;
801
802 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
803 loglvl, tsk->comm, task_pid_nr(tsk), address,
804 (void *)regs->ip, (void *)regs->sp, error_code);
805
806 print_vma_addr(KERN_CONT " in ", regs->ip);
807
808 /*
809 * Dump the likely CPU where the fatal segfault happened.
810 * This can help identify faulty hardware.
811 */
812 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
813 topology_core_id(cpu), topology_physical_package_id(cpu));
814
815
816 printk(KERN_CONT "\n");
817
818 show_opcodes(regs, loglvl);
819}
820
821/*
822 * The (legacy) vsyscall page is the long page in the kernel portion
823 * of the address space that has user-accessible permissions.
824 */
825static bool is_vsyscall_vaddr(unsigned long vaddr)
826{
827 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
828}
829
830static void
831__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
832 unsigned long address, u32 pkey, int si_code)
833{
834 struct task_struct *tsk = current;
835
836 if (!user_mode(regs)) {
837 kernelmode_fixup_or_oops(regs, error_code, address,
838 SIGSEGV, si_code, pkey);
839 return;
840 }
841
842 if (!(error_code & X86_PF_USER)) {
843 /* Implicit user access to kernel memory -- just oops */
844 page_fault_oops(regs, error_code, address);
845 return;
846 }
847
848 /*
849 * User mode accesses just cause a SIGSEGV.
850 * It's possible to have interrupts off here:
851 */
852 local_irq_enable();
853
854 /*
855 * Valid to do another page fault here because this one came
856 * from user space:
857 */
858 if (is_prefetch(regs, error_code, address))
859 return;
860
861 if (is_errata100(regs, address))
862 return;
863
864 sanitize_error_code(address, &error_code);
865
866 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
867 return;
868
869 if (likely(show_unhandled_signals))
870 show_signal_msg(regs, error_code, address, tsk);
871
872 set_signal_archinfo(address, error_code);
873
874 if (si_code == SEGV_PKUERR)
875 force_sig_pkuerr((void __user *)address, pkey);
876 else
877 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
878
879 local_irq_disable();
880}
881
882static noinline void
883bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
884 unsigned long address)
885{
886 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
887}
888
889static void
890__bad_area(struct pt_regs *regs, unsigned long error_code,
891 unsigned long address, u32 pkey, int si_code)
892{
893 struct mm_struct *mm = current->mm;
894 /*
895 * Something tried to access memory that isn't in our memory map..
896 * Fix it, but check if it's kernel or user first..
897 */
898 mmap_read_unlock(mm);
899
900 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
901}
902
903static noinline void
904bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
905{
906 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
907}
908
909static inline bool bad_area_access_from_pkeys(unsigned long error_code,
910 struct vm_area_struct *vma)
911{
912 /* This code is always called on the current mm */
913 bool foreign = false;
914
915 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
916 return false;
917 if (error_code & X86_PF_PK)
918 return true;
919 /* this checks permission keys on the VMA: */
920 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
921 (error_code & X86_PF_INSTR), foreign))
922 return true;
923 return false;
924}
925
926static noinline void
927bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
928 unsigned long address, struct vm_area_struct *vma)
929{
930 /*
931 * This OSPKE check is not strictly necessary at runtime.
932 * But, doing it this way allows compiler optimizations
933 * if pkeys are compiled out.
934 */
935 if (bad_area_access_from_pkeys(error_code, vma)) {
936 /*
937 * A protection key fault means that the PKRU value did not allow
938 * access to some PTE. Userspace can figure out what PKRU was
939 * from the XSAVE state. This function captures the pkey from
940 * the vma and passes it to userspace so userspace can discover
941 * which protection key was set on the PTE.
942 *
943 * If we get here, we know that the hardware signaled a X86_PF_PK
944 * fault and that there was a VMA once we got in the fault
945 * handler. It does *not* guarantee that the VMA we find here
946 * was the one that we faulted on.
947 *
948 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
949 * 2. T1 : set PKRU to deny access to pkey=4, touches page
950 * 3. T1 : faults...
951 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
952 * 5. T1 : enters fault handler, takes mmap_lock, etc...
953 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
954 * faulted on a pte with its pkey=4.
955 */
956 u32 pkey = vma_pkey(vma);
957
958 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
959 } else {
960 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
961 }
962}
963
964static void
965do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
966 vm_fault_t fault)
967{
968 /* Kernel mode? Handle exceptions or die: */
969 if (!user_mode(regs)) {
970 kernelmode_fixup_or_oops(regs, error_code, address,
971 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
972 return;
973 }
974
975 /* User-space => ok to do another page fault: */
976 if (is_prefetch(regs, error_code, address))
977 return;
978
979 sanitize_error_code(address, &error_code);
980
981 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
982 return;
983
984 set_signal_archinfo(address, error_code);
985
986#ifdef CONFIG_MEMORY_FAILURE
987 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
988 struct task_struct *tsk = current;
989 unsigned lsb = 0;
990
991 pr_err(
992 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
993 tsk->comm, tsk->pid, address);
994 if (fault & VM_FAULT_HWPOISON_LARGE)
995 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
996 if (fault & VM_FAULT_HWPOISON)
997 lsb = PAGE_SHIFT;
998 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
999 return;
1000 }
1001#endif
1002 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
1003}
1004
1005static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
1006{
1007 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
1008 return 0;
1009
1010 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
1011 return 0;
1012
1013 return 1;
1014}
1015
1016/*
1017 * Handle a spurious fault caused by a stale TLB entry.
1018 *
1019 * This allows us to lazily refresh the TLB when increasing the
1020 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1021 * eagerly is very expensive since that implies doing a full
1022 * cross-processor TLB flush, even if no stale TLB entries exist
1023 * on other processors.
1024 *
1025 * Spurious faults may only occur if the TLB contains an entry with
1026 * fewer permission than the page table entry. Non-present (P = 0)
1027 * and reserved bit (R = 1) faults are never spurious.
1028 *
1029 * There are no security implications to leaving a stale TLB when
1030 * increasing the permissions on a page.
1031 *
1032 * Returns non-zero if a spurious fault was handled, zero otherwise.
1033 *
1034 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1035 * (Optional Invalidation).
1036 */
1037static noinline int
1038spurious_kernel_fault(unsigned long error_code, unsigned long address)
1039{
1040 pgd_t *pgd;
1041 p4d_t *p4d;
1042 pud_t *pud;
1043 pmd_t *pmd;
1044 pte_t *pte;
1045 int ret;
1046
1047 /*
1048 * Only writes to RO or instruction fetches from NX may cause
1049 * spurious faults.
1050 *
1051 * These could be from user or supervisor accesses but the TLB
1052 * is only lazily flushed after a kernel mapping protection
1053 * change, so user accesses are not expected to cause spurious
1054 * faults.
1055 */
1056 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1057 error_code != (X86_PF_INSTR | X86_PF_PROT))
1058 return 0;
1059
1060 pgd = init_mm.pgd + pgd_index(address);
1061 if (!pgd_present(*pgd))
1062 return 0;
1063
1064 p4d = p4d_offset(pgd, address);
1065 if (!p4d_present(*p4d))
1066 return 0;
1067
1068 if (p4d_large(*p4d))
1069 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1070
1071 pud = pud_offset(p4d, address);
1072 if (!pud_present(*pud))
1073 return 0;
1074
1075 if (pud_large(*pud))
1076 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1077
1078 pmd = pmd_offset(pud, address);
1079 if (!pmd_present(*pmd))
1080 return 0;
1081
1082 if (pmd_large(*pmd))
1083 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1084
1085 pte = pte_offset_kernel(pmd, address);
1086 if (!pte_present(*pte))
1087 return 0;
1088
1089 ret = spurious_kernel_fault_check(error_code, pte);
1090 if (!ret)
1091 return 0;
1092
1093 /*
1094 * Make sure we have permissions in PMD.
1095 * If not, then there's a bug in the page tables:
1096 */
1097 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1098 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1099
1100 return ret;
1101}
1102NOKPROBE_SYMBOL(spurious_kernel_fault);
1103
1104int show_unhandled_signals = 1;
1105
1106static inline int
1107access_error(unsigned long error_code, struct vm_area_struct *vma)
1108{
1109 /* This is only called for the current mm, so: */
1110 bool foreign = false;
1111
1112 /*
1113 * Read or write was blocked by protection keys. This is
1114 * always an unconditional error and can never result in
1115 * a follow-up action to resolve the fault, like a COW.
1116 */
1117 if (error_code & X86_PF_PK)
1118 return 1;
1119
1120 /*
1121 * SGX hardware blocked the access. This usually happens
1122 * when the enclave memory contents have been destroyed, like
1123 * after a suspend/resume cycle. In any case, the kernel can't
1124 * fix the cause of the fault. Handle the fault as an access
1125 * error even in cases where no actual access violation
1126 * occurred. This allows userspace to rebuild the enclave in
1127 * response to the signal.
1128 */
1129 if (unlikely(error_code & X86_PF_SGX))
1130 return 1;
1131
1132 /*
1133 * Make sure to check the VMA so that we do not perform
1134 * faults just to hit a X86_PF_PK as soon as we fill in a
1135 * page.
1136 */
1137 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1138 (error_code & X86_PF_INSTR), foreign))
1139 return 1;
1140
1141 if (error_code & X86_PF_WRITE) {
1142 /* write, present and write, not present: */
1143 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1144 return 1;
1145 return 0;
1146 }
1147
1148 /* read, present: */
1149 if (unlikely(error_code & X86_PF_PROT))
1150 return 1;
1151
1152 /* read, not present: */
1153 if (unlikely(!vma_is_accessible(vma)))
1154 return 1;
1155
1156 return 0;
1157}
1158
1159bool fault_in_kernel_space(unsigned long address)
1160{
1161 /*
1162 * On 64-bit systems, the vsyscall page is at an address above
1163 * TASK_SIZE_MAX, but is not considered part of the kernel
1164 * address space.
1165 */
1166 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1167 return false;
1168
1169 return address >= TASK_SIZE_MAX;
1170}
1171
1172/*
1173 * Called for all faults where 'address' is part of the kernel address
1174 * space. Might get called for faults that originate from *code* that
1175 * ran in userspace or the kernel.
1176 */
1177static void
1178do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1179 unsigned long address)
1180{
1181 /*
1182 * Protection keys exceptions only happen on user pages. We
1183 * have no user pages in the kernel portion of the address
1184 * space, so do not expect them here.
1185 */
1186 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1187
1188#ifdef CONFIG_X86_32
1189 /*
1190 * We can fault-in kernel-space virtual memory on-demand. The
1191 * 'reference' page table is init_mm.pgd.
1192 *
1193 * NOTE! We MUST NOT take any locks for this case. We may
1194 * be in an interrupt or a critical region, and should
1195 * only copy the information from the master page table,
1196 * nothing more.
1197 *
1198 * Before doing this on-demand faulting, ensure that the
1199 * fault is not any of the following:
1200 * 1. A fault on a PTE with a reserved bit set.
1201 * 2. A fault caused by a user-mode access. (Do not demand-
1202 * fault kernel memory due to user-mode accesses).
1203 * 3. A fault caused by a page-level protection violation.
1204 * (A demand fault would be on a non-present page which
1205 * would have X86_PF_PROT==0).
1206 *
1207 * This is only needed to close a race condition on x86-32 in
1208 * the vmalloc mapping/unmapping code. See the comment above
1209 * vmalloc_fault() for details. On x86-64 the race does not
1210 * exist as the vmalloc mappings don't need to be synchronized
1211 * there.
1212 */
1213 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1214 if (vmalloc_fault(address) >= 0)
1215 return;
1216 }
1217#endif
1218
1219 if (is_f00f_bug(regs, hw_error_code, address))
1220 return;
1221
1222 /* Was the fault spurious, caused by lazy TLB invalidation? */
1223 if (spurious_kernel_fault(hw_error_code, address))
1224 return;
1225
1226 /* kprobes don't want to hook the spurious faults: */
1227 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1228 return;
1229
1230 /*
1231 * Note, despite being a "bad area", there are quite a few
1232 * acceptable reasons to get here, such as erratum fixups
1233 * and handling kernel code that can fault, like get_user().
1234 *
1235 * Don't take the mm semaphore here. If we fixup a prefetch
1236 * fault we could otherwise deadlock:
1237 */
1238 bad_area_nosemaphore(regs, hw_error_code, address);
1239}
1240NOKPROBE_SYMBOL(do_kern_addr_fault);
1241
1242/*
1243 * Handle faults in the user portion of the address space. Nothing in here
1244 * should check X86_PF_USER without a specific justification: for almost
1245 * all purposes, we should treat a normal kernel access to user memory
1246 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1247 * The one exception is AC flag handling, which is, per the x86
1248 * architecture, special for WRUSS.
1249 */
1250static inline
1251void do_user_addr_fault(struct pt_regs *regs,
1252 unsigned long error_code,
1253 unsigned long address)
1254{
1255 struct vm_area_struct *vma;
1256 struct task_struct *tsk;
1257 struct mm_struct *mm;
1258 vm_fault_t fault;
1259 unsigned int flags = FAULT_FLAG_DEFAULT;
1260
1261 tsk = current;
1262 mm = tsk->mm;
1263
1264 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1265 /*
1266 * Whoops, this is kernel mode code trying to execute from
1267 * user memory. Unless this is AMD erratum #93, which
1268 * corrupts RIP such that it looks like a user address,
1269 * this is unrecoverable. Don't even try to look up the
1270 * VMA or look for extable entries.
1271 */
1272 if (is_errata93(regs, address))
1273 return;
1274
1275 page_fault_oops(regs, error_code, address);
1276 return;
1277 }
1278
1279 /* kprobes don't want to hook the spurious faults: */
1280 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1281 return;
1282
1283 /*
1284 * Reserved bits are never expected to be set on
1285 * entries in the user portion of the page tables.
1286 */
1287 if (unlikely(error_code & X86_PF_RSVD))
1288 pgtable_bad(regs, error_code, address);
1289
1290 /*
1291 * If SMAP is on, check for invalid kernel (supervisor) access to user
1292 * pages in the user address space. The odd case here is WRUSS,
1293 * which, according to the preliminary documentation, does not respect
1294 * SMAP and will have the USER bit set so, in all cases, SMAP
1295 * enforcement appears to be consistent with the USER bit.
1296 */
1297 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1298 !(error_code & X86_PF_USER) &&
1299 !(regs->flags & X86_EFLAGS_AC))) {
1300 /*
1301 * No extable entry here. This was a kernel access to an
1302 * invalid pointer. get_kernel_nofault() will not get here.
1303 */
1304 page_fault_oops(regs, error_code, address);
1305 return;
1306 }
1307
1308 /*
1309 * If we're in an interrupt, have no user context or are running
1310 * in a region with pagefaults disabled then we must not take the fault
1311 */
1312 if (unlikely(faulthandler_disabled() || !mm)) {
1313 bad_area_nosemaphore(regs, error_code, address);
1314 return;
1315 }
1316
1317 /*
1318 * It's safe to allow irq's after cr2 has been saved and the
1319 * vmalloc fault has been handled.
1320 *
1321 * User-mode registers count as a user access even for any
1322 * potential system fault or CPU buglet:
1323 */
1324 if (user_mode(regs)) {
1325 local_irq_enable();
1326 flags |= FAULT_FLAG_USER;
1327 } else {
1328 if (regs->flags & X86_EFLAGS_IF)
1329 local_irq_enable();
1330 }
1331
1332 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1333
1334 if (error_code & X86_PF_WRITE)
1335 flags |= FAULT_FLAG_WRITE;
1336 if (error_code & X86_PF_INSTR)
1337 flags |= FAULT_FLAG_INSTRUCTION;
1338
1339#ifdef CONFIG_X86_64
1340 /*
1341 * Faults in the vsyscall page might need emulation. The
1342 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1343 * considered to be part of the user address space.
1344 *
1345 * The vsyscall page does not have a "real" VMA, so do this
1346 * emulation before we go searching for VMAs.
1347 *
1348 * PKRU never rejects instruction fetches, so we don't need
1349 * to consider the PF_PK bit.
1350 */
1351 if (is_vsyscall_vaddr(address)) {
1352 if (emulate_vsyscall(error_code, regs, address))
1353 return;
1354 }
1355#endif
1356
1357 /*
1358 * Kernel-mode access to the user address space should only occur
1359 * on well-defined single instructions listed in the exception
1360 * tables. But, an erroneous kernel fault occurring outside one of
1361 * those areas which also holds mmap_lock might deadlock attempting
1362 * to validate the fault against the address space.
1363 *
1364 * Only do the expensive exception table search when we might be at
1365 * risk of a deadlock. This happens if we
1366 * 1. Failed to acquire mmap_lock, and
1367 * 2. The access did not originate in userspace.
1368 */
1369 if (unlikely(!mmap_read_trylock(mm))) {
1370 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1371 /*
1372 * Fault from code in kernel from
1373 * which we do not expect faults.
1374 */
1375 bad_area_nosemaphore(regs, error_code, address);
1376 return;
1377 }
1378retry:
1379 mmap_read_lock(mm);
1380 } else {
1381 /*
1382 * The above down_read_trylock() might have succeeded in
1383 * which case we'll have missed the might_sleep() from
1384 * down_read():
1385 */
1386 might_sleep();
1387 }
1388
1389 vma = find_vma(mm, address);
1390 if (unlikely(!vma)) {
1391 bad_area(regs, error_code, address);
1392 return;
1393 }
1394 if (likely(vma->vm_start <= address))
1395 goto good_area;
1396 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1397 bad_area(regs, error_code, address);
1398 return;
1399 }
1400 if (unlikely(expand_stack(vma, address))) {
1401 bad_area(regs, error_code, address);
1402 return;
1403 }
1404
1405 /*
1406 * Ok, we have a good vm_area for this memory access, so
1407 * we can handle it..
1408 */
1409good_area:
1410 if (unlikely(access_error(error_code, vma))) {
1411 bad_area_access_error(regs, error_code, address, vma);
1412 return;
1413 }
1414
1415 /*
1416 * If for any reason at all we couldn't handle the fault,
1417 * make sure we exit gracefully rather than endlessly redo
1418 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1419 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1420 *
1421 * Note that handle_userfault() may also release and reacquire mmap_lock
1422 * (and not return with VM_FAULT_RETRY), when returning to userland to
1423 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1424 * (potentially after handling any pending signal during the return to
1425 * userland). The return to userland is identified whenever
1426 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1427 */
1428 fault = handle_mm_fault(vma, address, flags, regs);
1429
1430 if (fault_signal_pending(fault, regs)) {
1431 /*
1432 * Quick path to respond to signals. The core mm code
1433 * has unlocked the mm for us if we get here.
1434 */
1435 if (!user_mode(regs))
1436 kernelmode_fixup_or_oops(regs, error_code, address,
1437 SIGBUS, BUS_ADRERR,
1438 ARCH_DEFAULT_PKEY);
1439 return;
1440 }
1441
1442 /* The fault is fully completed (including releasing mmap lock) */
1443 if (fault & VM_FAULT_COMPLETED)
1444 return;
1445
1446 /*
1447 * If we need to retry the mmap_lock has already been released,
1448 * and if there is a fatal signal pending there is no guarantee
1449 * that we made any progress. Handle this case first.
1450 */
1451 if (unlikely(fault & VM_FAULT_RETRY)) {
1452 flags |= FAULT_FLAG_TRIED;
1453 goto retry;
1454 }
1455
1456 mmap_read_unlock(mm);
1457 if (likely(!(fault & VM_FAULT_ERROR)))
1458 return;
1459
1460 if (fatal_signal_pending(current) && !user_mode(regs)) {
1461 kernelmode_fixup_or_oops(regs, error_code, address,
1462 0, 0, ARCH_DEFAULT_PKEY);
1463 return;
1464 }
1465
1466 if (fault & VM_FAULT_OOM) {
1467 /* Kernel mode? Handle exceptions or die: */
1468 if (!user_mode(regs)) {
1469 kernelmode_fixup_or_oops(regs, error_code, address,
1470 SIGSEGV, SEGV_MAPERR,
1471 ARCH_DEFAULT_PKEY);
1472 return;
1473 }
1474
1475 /*
1476 * We ran out of memory, call the OOM killer, and return the
1477 * userspace (which will retry the fault, or kill us if we got
1478 * oom-killed):
1479 */
1480 pagefault_out_of_memory();
1481 } else {
1482 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1483 VM_FAULT_HWPOISON_LARGE))
1484 do_sigbus(regs, error_code, address, fault);
1485 else if (fault & VM_FAULT_SIGSEGV)
1486 bad_area_nosemaphore(regs, error_code, address);
1487 else
1488 BUG();
1489 }
1490}
1491NOKPROBE_SYMBOL(do_user_addr_fault);
1492
1493static __always_inline void
1494trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1495 unsigned long address)
1496{
1497 if (!trace_pagefault_enabled())
1498 return;
1499
1500 if (user_mode(regs))
1501 trace_page_fault_user(address, regs, error_code);
1502 else
1503 trace_page_fault_kernel(address, regs, error_code);
1504}
1505
1506static __always_inline void
1507handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1508 unsigned long address)
1509{
1510 trace_page_fault_entries(regs, error_code, address);
1511
1512 if (unlikely(kmmio_fault(regs, address)))
1513 return;
1514
1515 /* Was the fault on kernel-controlled part of the address space? */
1516 if (unlikely(fault_in_kernel_space(address))) {
1517 do_kern_addr_fault(regs, error_code, address);
1518 } else {
1519 do_user_addr_fault(regs, error_code, address);
1520 /*
1521 * User address page fault handling might have reenabled
1522 * interrupts. Fixing up all potential exit points of
1523 * do_user_addr_fault() and its leaf functions is just not
1524 * doable w/o creating an unholy mess or turning the code
1525 * upside down.
1526 */
1527 local_irq_disable();
1528 }
1529}
1530
1531DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1532{
1533 unsigned long address = read_cr2();
1534 irqentry_state_t state;
1535
1536 prefetchw(¤t->mm->mmap_lock);
1537
1538 /*
1539 * KVM uses #PF vector to deliver 'page not present' events to guests
1540 * (asynchronous page fault mechanism). The event happens when a
1541 * userspace task is trying to access some valid (from guest's point of
1542 * view) memory which is not currently mapped by the host (e.g. the
1543 * memory is swapped out). Note, the corresponding "page ready" event
1544 * which is injected when the memory becomes available, is delivered via
1545 * an interrupt mechanism and not a #PF exception
1546 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1547 *
1548 * We are relying on the interrupted context being sane (valid RSP,
1549 * relevant locks not held, etc.), which is fine as long as the
1550 * interrupted context had IF=1. We are also relying on the KVM
1551 * async pf type field and CR2 being read consistently instead of
1552 * getting values from real and async page faults mixed up.
1553 *
1554 * Fingers crossed.
1555 *
1556 * The async #PF handling code takes care of idtentry handling
1557 * itself.
1558 */
1559 if (kvm_handle_async_pf(regs, (u32)address))
1560 return;
1561
1562 /*
1563 * Entry handling for valid #PF from kernel mode is slightly
1564 * different: RCU is already watching and ct_irq_enter() must not
1565 * be invoked because a kernel fault on a user space address might
1566 * sleep.
1567 *
1568 * In case the fault hit a RCU idle region the conditional entry
1569 * code reenabled RCU to avoid subsequent wreckage which helps
1570 * debuggability.
1571 */
1572 state = irqentry_enter(regs);
1573
1574 instrumentation_begin();
1575 handle_page_fault(regs, error_code, address);
1576 instrumentation_end();
1577
1578 irqentry_exit(regs, state);
1579}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1995 Linus Torvalds
4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 */
7#include <linux/sched.h> /* test_thread_flag(), ... */
8#include <linux/sched/task_stack.h> /* task_stack_*(), ... */
9#include <linux/kdebug.h> /* oops_begin/end, ... */
10#include <linux/extable.h> /* search_exception_tables */
11#include <linux/memblock.h> /* max_low_pfn */
12#include <linux/kfence.h> /* kfence_handle_page_fault */
13#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
14#include <linux/mmiotrace.h> /* kmmio_handler, ... */
15#include <linux/perf_event.h> /* perf_sw_event */
16#include <linux/hugetlb.h> /* hstate_index_to_shift */
17#include <linux/prefetch.h> /* prefetchw */
18#include <linux/context_tracking.h> /* exception_enter(), ... */
19#include <linux/uaccess.h> /* faulthandler_disabled() */
20#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
21#include <linux/mm_types.h>
22#include <linux/mm.h> /* find_and_lock_vma() */
23
24#include <asm/cpufeature.h> /* boot_cpu_has, ... */
25#include <asm/traps.h> /* dotraplinkage, ... */
26#include <asm/fixmap.h> /* VSYSCALL_ADDR */
27#include <asm/vsyscall.h> /* emulate_vsyscall */
28#include <asm/vm86.h> /* struct vm86 */
29#include <asm/mmu_context.h> /* vma_pkey() */
30#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
31#include <asm/desc.h> /* store_idt(), ... */
32#include <asm/cpu_entry_area.h> /* exception stack */
33#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
34#include <asm/kvm_para.h> /* kvm_handle_async_pf */
35#include <asm/vdso.h> /* fixup_vdso_exception() */
36#include <asm/irq_stack.h>
37#include <asm/fred.h>
38#include <asm/sev.h> /* snp_dump_hva_rmpentry() */
39
40#define CREATE_TRACE_POINTS
41#include <asm/trace/exceptions.h>
42
43/*
44 * Returns 0 if mmiotrace is disabled, or if the fault is not
45 * handled by mmiotrace:
46 */
47static nokprobe_inline int
48kmmio_fault(struct pt_regs *regs, unsigned long addr)
49{
50 if (unlikely(is_kmmio_active()))
51 if (kmmio_handler(regs, addr) == 1)
52 return -1;
53 return 0;
54}
55
56/*
57 * Prefetch quirks:
58 *
59 * 32-bit mode:
60 *
61 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
62 * Check that here and ignore it. This is AMD erratum #91.
63 *
64 * 64-bit mode:
65 *
66 * Sometimes the CPU reports invalid exceptions on prefetch.
67 * Check that here and ignore it.
68 *
69 * Opcode checker based on code by Richard Brunner.
70 */
71static inline int
72check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
73 unsigned char opcode, int *prefetch)
74{
75 unsigned char instr_hi = opcode & 0xf0;
76 unsigned char instr_lo = opcode & 0x0f;
77
78 switch (instr_hi) {
79 case 0x20:
80 case 0x30:
81 /*
82 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
83 * In X86_64 long mode, the CPU will signal invalid
84 * opcode if some of these prefixes are present so
85 * X86_64 will never get here anyway
86 */
87 return ((instr_lo & 7) == 0x6);
88#ifdef CONFIG_X86_64
89 case 0x40:
90 /*
91 * In 64-bit mode 0x40..0x4F are valid REX prefixes
92 */
93 return (!user_mode(regs) || user_64bit_mode(regs));
94#endif
95 case 0x60:
96 /* 0x64 thru 0x67 are valid prefixes in all modes. */
97 return (instr_lo & 0xC) == 0x4;
98 case 0xF0:
99 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
100 return !instr_lo || (instr_lo>>1) == 1;
101 case 0x00:
102 /* Prefetch instruction is 0x0F0D or 0x0F18 */
103 if (get_kernel_nofault(opcode, instr))
104 return 0;
105
106 *prefetch = (instr_lo == 0xF) &&
107 (opcode == 0x0D || opcode == 0x18);
108 return 0;
109 default:
110 return 0;
111 }
112}
113
114static bool is_amd_k8_pre_npt(void)
115{
116 struct cpuinfo_x86 *c = &boot_cpu_data;
117
118 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
119 c->x86_vendor == X86_VENDOR_AMD &&
120 c->x86 == 0xf && c->x86_model < 0x40);
121}
122
123static int
124is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
125{
126 unsigned char *max_instr;
127 unsigned char *instr;
128 int prefetch = 0;
129
130 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
131 if (!is_amd_k8_pre_npt())
132 return 0;
133
134 /*
135 * If it was a exec (instruction fetch) fault on NX page, then
136 * do not ignore the fault:
137 */
138 if (error_code & X86_PF_INSTR)
139 return 0;
140
141 instr = (void *)convert_ip_to_linear(current, regs);
142 max_instr = instr + 15;
143
144 /*
145 * This code has historically always bailed out if IP points to a
146 * not-present page (e.g. due to a race). No one has ever
147 * complained about this.
148 */
149 pagefault_disable();
150
151 while (instr < max_instr) {
152 unsigned char opcode;
153
154 if (user_mode(regs)) {
155 if (get_user(opcode, (unsigned char __user *) instr))
156 break;
157 } else {
158 if (get_kernel_nofault(opcode, instr))
159 break;
160 }
161
162 instr++;
163
164 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
165 break;
166 }
167
168 pagefault_enable();
169 return prefetch;
170}
171
172DEFINE_SPINLOCK(pgd_lock);
173LIST_HEAD(pgd_list);
174
175#ifdef CONFIG_X86_32
176static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
177{
178 unsigned index = pgd_index(address);
179 pgd_t *pgd_k;
180 p4d_t *p4d, *p4d_k;
181 pud_t *pud, *pud_k;
182 pmd_t *pmd, *pmd_k;
183
184 pgd += index;
185 pgd_k = init_mm.pgd + index;
186
187 if (!pgd_present(*pgd_k))
188 return NULL;
189
190 /*
191 * set_pgd(pgd, *pgd_k); here would be useless on PAE
192 * and redundant with the set_pmd() on non-PAE. As would
193 * set_p4d/set_pud.
194 */
195 p4d = p4d_offset(pgd, address);
196 p4d_k = p4d_offset(pgd_k, address);
197 if (!p4d_present(*p4d_k))
198 return NULL;
199
200 pud = pud_offset(p4d, address);
201 pud_k = pud_offset(p4d_k, address);
202 if (!pud_present(*pud_k))
203 return NULL;
204
205 pmd = pmd_offset(pud, address);
206 pmd_k = pmd_offset(pud_k, address);
207
208 if (pmd_present(*pmd) != pmd_present(*pmd_k))
209 set_pmd(pmd, *pmd_k);
210
211 if (!pmd_present(*pmd_k))
212 return NULL;
213 else
214 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
215
216 return pmd_k;
217}
218
219/*
220 * Handle a fault on the vmalloc or module mapping area
221 *
222 * This is needed because there is a race condition between the time
223 * when the vmalloc mapping code updates the PMD to the point in time
224 * where it synchronizes this update with the other page-tables in the
225 * system.
226 *
227 * In this race window another thread/CPU can map an area on the same
228 * PMD, finds it already present and does not synchronize it with the
229 * rest of the system yet. As a result v[mz]alloc might return areas
230 * which are not mapped in every page-table in the system, causing an
231 * unhandled page-fault when they are accessed.
232 */
233static noinline int vmalloc_fault(unsigned long address)
234{
235 unsigned long pgd_paddr;
236 pmd_t *pmd_k;
237 pte_t *pte_k;
238
239 /* Make sure we are in vmalloc area: */
240 if (!(address >= VMALLOC_START && address < VMALLOC_END))
241 return -1;
242
243 /*
244 * Synchronize this task's top level page-table
245 * with the 'reference' page table.
246 *
247 * Do _not_ use "current" here. We might be inside
248 * an interrupt in the middle of a task switch..
249 */
250 pgd_paddr = read_cr3_pa();
251 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
252 if (!pmd_k)
253 return -1;
254
255 if (pmd_leaf(*pmd_k))
256 return 0;
257
258 pte_k = pte_offset_kernel(pmd_k, address);
259 if (!pte_present(*pte_k))
260 return -1;
261
262 return 0;
263}
264NOKPROBE_SYMBOL(vmalloc_fault);
265
266void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
267{
268 unsigned long addr;
269
270 for (addr = start & PMD_MASK;
271 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
272 addr += PMD_SIZE) {
273 struct page *page;
274
275 spin_lock(&pgd_lock);
276 list_for_each_entry(page, &pgd_list, lru) {
277 spinlock_t *pgt_lock;
278
279 /* the pgt_lock only for Xen */
280 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
281
282 spin_lock(pgt_lock);
283 vmalloc_sync_one(page_address(page), addr);
284 spin_unlock(pgt_lock);
285 }
286 spin_unlock(&pgd_lock);
287 }
288}
289
290static bool low_pfn(unsigned long pfn)
291{
292 return pfn < max_low_pfn;
293}
294
295static void dump_pagetable(unsigned long address)
296{
297 pgd_t *base = __va(read_cr3_pa());
298 pgd_t *pgd = &base[pgd_index(address)];
299 p4d_t *p4d;
300 pud_t *pud;
301 pmd_t *pmd;
302 pte_t *pte;
303
304#ifdef CONFIG_X86_PAE
305 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
306 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
307 goto out;
308#define pr_pde pr_cont
309#else
310#define pr_pde pr_info
311#endif
312 p4d = p4d_offset(pgd, address);
313 pud = pud_offset(p4d, address);
314 pmd = pmd_offset(pud, address);
315 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
316#undef pr_pde
317
318 /*
319 * We must not directly access the pte in the highpte
320 * case if the page table is located in highmem.
321 * And let's rather not kmap-atomic the pte, just in case
322 * it's allocated already:
323 */
324 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_leaf(*pmd))
325 goto out;
326
327 pte = pte_offset_kernel(pmd, address);
328 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
329out:
330 pr_cont("\n");
331}
332
333#else /* CONFIG_X86_64: */
334
335#ifdef CONFIG_CPU_SUP_AMD
336static const char errata93_warning[] =
337KERN_ERR
338"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
339"******* Working around it, but it may cause SEGVs or burn power.\n"
340"******* Please consider a BIOS update.\n"
341"******* Disabling USB legacy in the BIOS may also help.\n";
342#endif
343
344static int bad_address(void *p)
345{
346 unsigned long dummy;
347
348 return get_kernel_nofault(dummy, (unsigned long *)p);
349}
350
351static void dump_pagetable(unsigned long address)
352{
353 pgd_t *base = __va(read_cr3_pa());
354 pgd_t *pgd = base + pgd_index(address);
355 p4d_t *p4d;
356 pud_t *pud;
357 pmd_t *pmd;
358 pte_t *pte;
359
360 if (bad_address(pgd))
361 goto bad;
362
363 pr_info("PGD %lx ", pgd_val(*pgd));
364
365 if (!pgd_present(*pgd))
366 goto out;
367
368 p4d = p4d_offset(pgd, address);
369 if (bad_address(p4d))
370 goto bad;
371
372 pr_cont("P4D %lx ", p4d_val(*p4d));
373 if (!p4d_present(*p4d) || p4d_leaf(*p4d))
374 goto out;
375
376 pud = pud_offset(p4d, address);
377 if (bad_address(pud))
378 goto bad;
379
380 pr_cont("PUD %lx ", pud_val(*pud));
381 if (!pud_present(*pud) || pud_leaf(*pud))
382 goto out;
383
384 pmd = pmd_offset(pud, address);
385 if (bad_address(pmd))
386 goto bad;
387
388 pr_cont("PMD %lx ", pmd_val(*pmd));
389 if (!pmd_present(*pmd) || pmd_leaf(*pmd))
390 goto out;
391
392 pte = pte_offset_kernel(pmd, address);
393 if (bad_address(pte))
394 goto bad;
395
396 pr_cont("PTE %lx", pte_val(*pte));
397out:
398 pr_cont("\n");
399 return;
400bad:
401 pr_info("BAD\n");
402}
403
404#endif /* CONFIG_X86_64 */
405
406/*
407 * Workaround for K8 erratum #93 & buggy BIOS.
408 *
409 * BIOS SMM functions are required to use a specific workaround
410 * to avoid corruption of the 64bit RIP register on C stepping K8.
411 *
412 * A lot of BIOS that didn't get tested properly miss this.
413 *
414 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
415 * Try to work around it here.
416 *
417 * Note we only handle faults in kernel here.
418 * Does nothing on 32-bit.
419 */
420static int is_errata93(struct pt_regs *regs, unsigned long address)
421{
422#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
423 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
424 || boot_cpu_data.x86 != 0xf)
425 return 0;
426
427 if (user_mode(regs))
428 return 0;
429
430 if (address != regs->ip)
431 return 0;
432
433 if ((address >> 32) != 0)
434 return 0;
435
436 address |= 0xffffffffUL << 32;
437 if ((address >= (u64)_stext && address <= (u64)_etext) ||
438 (address >= MODULES_VADDR && address <= MODULES_END)) {
439 printk_once(errata93_warning);
440 regs->ip = address;
441 return 1;
442 }
443#endif
444 return 0;
445}
446
447/*
448 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
449 * to illegal addresses >4GB.
450 *
451 * We catch this in the page fault handler because these addresses
452 * are not reachable. Just detect this case and return. Any code
453 * segment in LDT is compatibility mode.
454 */
455static int is_errata100(struct pt_regs *regs, unsigned long address)
456{
457#ifdef CONFIG_X86_64
458 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
459 return 1;
460#endif
461 return 0;
462}
463
464/* Pentium F0 0F C7 C8 bug workaround: */
465static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
466 unsigned long address)
467{
468#ifdef CONFIG_X86_F00F_BUG
469 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
470 idt_is_f00f_address(address)) {
471 handle_invalid_op(regs);
472 return 1;
473 }
474#endif
475 return 0;
476}
477
478static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
479{
480 u32 offset = (index >> 3) * sizeof(struct desc_struct);
481 unsigned long addr;
482 struct ldttss_desc desc;
483
484 if (index == 0) {
485 pr_alert("%s: NULL\n", name);
486 return;
487 }
488
489 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
490 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
491 return;
492 }
493
494 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
495 sizeof(struct ldttss_desc))) {
496 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
497 name, index);
498 return;
499 }
500
501 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
502#ifdef CONFIG_X86_64
503 addr |= ((u64)desc.base3 << 32);
504#endif
505 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
506 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
507}
508
509static void
510show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
511{
512 if (!oops_may_print())
513 return;
514
515 if (error_code & X86_PF_INSTR) {
516 unsigned int level;
517 pgd_t *pgd;
518 pte_t *pte;
519
520 pgd = __va(read_cr3_pa());
521 pgd += pgd_index(address);
522
523 pte = lookup_address_in_pgd(pgd, address, &level);
524
525 if (pte && pte_present(*pte) && !pte_exec(*pte))
526 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
527 from_kuid(&init_user_ns, current_uid()));
528 if (pte && pte_present(*pte) && pte_exec(*pte) &&
529 (pgd_flags(*pgd) & _PAGE_USER) &&
530 (__read_cr4() & X86_CR4_SMEP))
531 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
532 from_kuid(&init_user_ns, current_uid()));
533 }
534
535 if (address < PAGE_SIZE && !user_mode(regs))
536 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
537 (void *)address);
538 else
539 pr_alert("BUG: unable to handle page fault for address: %px\n",
540 (void *)address);
541
542 pr_alert("#PF: %s %s in %s mode\n",
543 (error_code & X86_PF_USER) ? "user" : "supervisor",
544 (error_code & X86_PF_INSTR) ? "instruction fetch" :
545 (error_code & X86_PF_WRITE) ? "write access" :
546 "read access",
547 user_mode(regs) ? "user" : "kernel");
548 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
549 !(error_code & X86_PF_PROT) ? "not-present page" :
550 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
551 (error_code & X86_PF_PK) ? "protection keys violation" :
552 (error_code & X86_PF_RMP) ? "RMP violation" :
553 "permissions violation");
554
555 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
556 struct desc_ptr idt, gdt;
557 u16 ldtr, tr;
558
559 /*
560 * This can happen for quite a few reasons. The more obvious
561 * ones are faults accessing the GDT, or LDT. Perhaps
562 * surprisingly, if the CPU tries to deliver a benign or
563 * contributory exception from user code and gets a page fault
564 * during delivery, the page fault can be delivered as though
565 * it originated directly from user code. This could happen
566 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
567 * kernel or IST stack.
568 */
569 store_idt(&idt);
570
571 /* Usable even on Xen PV -- it's just slow. */
572 native_store_gdt(&gdt);
573
574 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
575 idt.address, idt.size, gdt.address, gdt.size);
576
577 store_ldt(ldtr);
578 show_ldttss(&gdt, "LDTR", ldtr);
579
580 store_tr(tr);
581 show_ldttss(&gdt, "TR", tr);
582 }
583
584 dump_pagetable(address);
585
586 if (error_code & X86_PF_RMP)
587 snp_dump_hva_rmpentry(address);
588}
589
590static noinline void
591pgtable_bad(struct pt_regs *regs, unsigned long error_code,
592 unsigned long address)
593{
594 struct task_struct *tsk;
595 unsigned long flags;
596 int sig;
597
598 flags = oops_begin();
599 tsk = current;
600 sig = SIGKILL;
601
602 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
603 tsk->comm, address);
604 dump_pagetable(address);
605
606 if (__die("Bad pagetable", regs, error_code))
607 sig = 0;
608
609 oops_end(flags, regs, sig);
610}
611
612static void sanitize_error_code(unsigned long address,
613 unsigned long *error_code)
614{
615 /*
616 * To avoid leaking information about the kernel page
617 * table layout, pretend that user-mode accesses to
618 * kernel addresses are always protection faults.
619 *
620 * NB: This means that failed vsyscalls with vsyscall=none
621 * will have the PROT bit. This doesn't leak any
622 * information and does not appear to cause any problems.
623 */
624 if (address >= TASK_SIZE_MAX)
625 *error_code |= X86_PF_PROT;
626}
627
628static void set_signal_archinfo(unsigned long address,
629 unsigned long error_code)
630{
631 struct task_struct *tsk = current;
632
633 tsk->thread.trap_nr = X86_TRAP_PF;
634 tsk->thread.error_code = error_code | X86_PF_USER;
635 tsk->thread.cr2 = address;
636}
637
638static noinline void
639page_fault_oops(struct pt_regs *regs, unsigned long error_code,
640 unsigned long address)
641{
642#ifdef CONFIG_VMAP_STACK
643 struct stack_info info;
644#endif
645 unsigned long flags;
646 int sig;
647
648 if (user_mode(regs)) {
649 /*
650 * Implicit kernel access from user mode? Skip the stack
651 * overflow and EFI special cases.
652 */
653 goto oops;
654 }
655
656#ifdef CONFIG_VMAP_STACK
657 /*
658 * Stack overflow? During boot, we can fault near the initial
659 * stack in the direct map, but that's not an overflow -- check
660 * that we're in vmalloc space to avoid this.
661 */
662 if (is_vmalloc_addr((void *)address) &&
663 get_stack_guard_info((void *)address, &info)) {
664 /*
665 * We're likely to be running with very little stack space
666 * left. It's plausible that we'd hit this condition but
667 * double-fault even before we get this far, in which case
668 * we're fine: the double-fault handler will deal with it.
669 *
670 * We don't want to make it all the way into the oops code
671 * and then double-fault, though, because we're likely to
672 * break the console driver and lose most of the stack dump.
673 */
674 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
675 handle_stack_overflow,
676 ASM_CALL_ARG3,
677 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
678
679 unreachable();
680 }
681#endif
682
683 /*
684 * Buggy firmware could access regions which might page fault. If
685 * this happens, EFI has a special OOPS path that will try to
686 * avoid hanging the system.
687 */
688 if (IS_ENABLED(CONFIG_EFI))
689 efi_crash_gracefully_on_page_fault(address);
690
691 /* Only not-present faults should be handled by KFENCE. */
692 if (!(error_code & X86_PF_PROT) &&
693 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
694 return;
695
696oops:
697 /*
698 * Oops. The kernel tried to access some bad page. We'll have to
699 * terminate things with extreme prejudice:
700 */
701 flags = oops_begin();
702
703 show_fault_oops(regs, error_code, address);
704
705 if (task_stack_end_corrupted(current))
706 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
707
708 sig = SIGKILL;
709 if (__die("Oops", regs, error_code))
710 sig = 0;
711
712 /* Executive summary in case the body of the oops scrolled away */
713 printk(KERN_DEFAULT "CR2: %016lx\n", address);
714
715 oops_end(flags, regs, sig);
716}
717
718static noinline void
719kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
720 unsigned long address, int signal, int si_code,
721 u32 pkey)
722{
723 WARN_ON_ONCE(user_mode(regs));
724
725 /* Are we prepared to handle this kernel fault? */
726 if (fixup_exception(regs, X86_TRAP_PF, error_code, address))
727 return;
728
729 /*
730 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
731 * instruction.
732 */
733 if (is_prefetch(regs, error_code, address))
734 return;
735
736 page_fault_oops(regs, error_code, address);
737}
738
739/*
740 * Print out info about fatal segfaults, if the show_unhandled_signals
741 * sysctl is set:
742 */
743static inline void
744show_signal_msg(struct pt_regs *regs, unsigned long error_code,
745 unsigned long address, struct task_struct *tsk)
746{
747 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
748 /* This is a racy snapshot, but it's better than nothing. */
749 int cpu = raw_smp_processor_id();
750
751 if (!unhandled_signal(tsk, SIGSEGV))
752 return;
753
754 if (!printk_ratelimit())
755 return;
756
757 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
758 loglvl, tsk->comm, task_pid_nr(tsk), address,
759 (void *)regs->ip, (void *)regs->sp, error_code);
760
761 print_vma_addr(KERN_CONT " in ", regs->ip);
762
763 /*
764 * Dump the likely CPU where the fatal segfault happened.
765 * This can help identify faulty hardware.
766 */
767 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
768 topology_core_id(cpu), topology_physical_package_id(cpu));
769
770
771 printk(KERN_CONT "\n");
772
773 show_opcodes(regs, loglvl);
774}
775
776static void
777__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
778 unsigned long address, u32 pkey, int si_code)
779{
780 struct task_struct *tsk = current;
781
782 if (!user_mode(regs)) {
783 kernelmode_fixup_or_oops(regs, error_code, address,
784 SIGSEGV, si_code, pkey);
785 return;
786 }
787
788 if (!(error_code & X86_PF_USER)) {
789 /* Implicit user access to kernel memory -- just oops */
790 page_fault_oops(regs, error_code, address);
791 return;
792 }
793
794 /*
795 * User mode accesses just cause a SIGSEGV.
796 * It's possible to have interrupts off here:
797 */
798 local_irq_enable();
799
800 /*
801 * Valid to do another page fault here because this one came
802 * from user space:
803 */
804 if (is_prefetch(regs, error_code, address))
805 return;
806
807 if (is_errata100(regs, address))
808 return;
809
810 sanitize_error_code(address, &error_code);
811
812 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
813 return;
814
815 if (likely(show_unhandled_signals))
816 show_signal_msg(regs, error_code, address, tsk);
817
818 set_signal_archinfo(address, error_code);
819
820 if (si_code == SEGV_PKUERR)
821 force_sig_pkuerr((void __user *)address, pkey);
822 else
823 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
824
825 local_irq_disable();
826}
827
828static noinline void
829bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
830 unsigned long address)
831{
832 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
833}
834
835static void
836__bad_area(struct pt_regs *regs, unsigned long error_code,
837 unsigned long address, u32 pkey, int si_code)
838{
839 struct mm_struct *mm = current->mm;
840 /*
841 * Something tried to access memory that isn't in our memory map..
842 * Fix it, but check if it's kernel or user first..
843 */
844 mmap_read_unlock(mm);
845
846 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
847}
848
849static inline bool bad_area_access_from_pkeys(unsigned long error_code,
850 struct vm_area_struct *vma)
851{
852 /* This code is always called on the current mm */
853 bool foreign = false;
854
855 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
856 return false;
857 if (error_code & X86_PF_PK)
858 return true;
859 /* this checks permission keys on the VMA: */
860 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
861 (error_code & X86_PF_INSTR), foreign))
862 return true;
863 return false;
864}
865
866static noinline void
867bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
868 unsigned long address, struct vm_area_struct *vma)
869{
870 /*
871 * This OSPKE check is not strictly necessary at runtime.
872 * But, doing it this way allows compiler optimizations
873 * if pkeys are compiled out.
874 */
875 if (bad_area_access_from_pkeys(error_code, vma)) {
876 /*
877 * A protection key fault means that the PKRU value did not allow
878 * access to some PTE. Userspace can figure out what PKRU was
879 * from the XSAVE state. This function captures the pkey from
880 * the vma and passes it to userspace so userspace can discover
881 * which protection key was set on the PTE.
882 *
883 * If we get here, we know that the hardware signaled a X86_PF_PK
884 * fault and that there was a VMA once we got in the fault
885 * handler. It does *not* guarantee that the VMA we find here
886 * was the one that we faulted on.
887 *
888 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
889 * 2. T1 : set PKRU to deny access to pkey=4, touches page
890 * 3. T1 : faults...
891 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
892 * 5. T1 : enters fault handler, takes mmap_lock, etc...
893 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
894 * faulted on a pte with its pkey=4.
895 */
896 u32 pkey = vma_pkey(vma);
897
898 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
899 } else {
900 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
901 }
902}
903
904static void
905do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
906 vm_fault_t fault)
907{
908 /* Kernel mode? Handle exceptions or die: */
909 if (!user_mode(regs)) {
910 kernelmode_fixup_or_oops(regs, error_code, address,
911 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
912 return;
913 }
914
915 /* User-space => ok to do another page fault: */
916 if (is_prefetch(regs, error_code, address))
917 return;
918
919 sanitize_error_code(address, &error_code);
920
921 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
922 return;
923
924 set_signal_archinfo(address, error_code);
925
926#ifdef CONFIG_MEMORY_FAILURE
927 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
928 struct task_struct *tsk = current;
929 unsigned lsb = 0;
930
931 pr_err(
932 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
933 tsk->comm, tsk->pid, address);
934 if (fault & VM_FAULT_HWPOISON_LARGE)
935 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
936 if (fault & VM_FAULT_HWPOISON)
937 lsb = PAGE_SHIFT;
938 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
939 return;
940 }
941#endif
942 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
943}
944
945static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
946{
947 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
948 return 0;
949
950 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
951 return 0;
952
953 return 1;
954}
955
956/*
957 * Handle a spurious fault caused by a stale TLB entry.
958 *
959 * This allows us to lazily refresh the TLB when increasing the
960 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
961 * eagerly is very expensive since that implies doing a full
962 * cross-processor TLB flush, even if no stale TLB entries exist
963 * on other processors.
964 *
965 * Spurious faults may only occur if the TLB contains an entry with
966 * fewer permission than the page table entry. Non-present (P = 0)
967 * and reserved bit (R = 1) faults are never spurious.
968 *
969 * There are no security implications to leaving a stale TLB when
970 * increasing the permissions on a page.
971 *
972 * Returns non-zero if a spurious fault was handled, zero otherwise.
973 *
974 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
975 * (Optional Invalidation).
976 */
977static noinline int
978spurious_kernel_fault(unsigned long error_code, unsigned long address)
979{
980 pgd_t *pgd;
981 p4d_t *p4d;
982 pud_t *pud;
983 pmd_t *pmd;
984 pte_t *pte;
985 int ret;
986
987 /*
988 * Only writes to RO or instruction fetches from NX may cause
989 * spurious faults.
990 *
991 * These could be from user or supervisor accesses but the TLB
992 * is only lazily flushed after a kernel mapping protection
993 * change, so user accesses are not expected to cause spurious
994 * faults.
995 */
996 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
997 error_code != (X86_PF_INSTR | X86_PF_PROT))
998 return 0;
999
1000 pgd = init_mm.pgd + pgd_index(address);
1001 if (!pgd_present(*pgd))
1002 return 0;
1003
1004 p4d = p4d_offset(pgd, address);
1005 if (!p4d_present(*p4d))
1006 return 0;
1007
1008 if (p4d_leaf(*p4d))
1009 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1010
1011 pud = pud_offset(p4d, address);
1012 if (!pud_present(*pud))
1013 return 0;
1014
1015 if (pud_leaf(*pud))
1016 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1017
1018 pmd = pmd_offset(pud, address);
1019 if (!pmd_present(*pmd))
1020 return 0;
1021
1022 if (pmd_leaf(*pmd))
1023 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1024
1025 pte = pte_offset_kernel(pmd, address);
1026 if (!pte_present(*pte))
1027 return 0;
1028
1029 ret = spurious_kernel_fault_check(error_code, pte);
1030 if (!ret)
1031 return 0;
1032
1033 /*
1034 * Make sure we have permissions in PMD.
1035 * If not, then there's a bug in the page tables:
1036 */
1037 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1038 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1039
1040 return ret;
1041}
1042NOKPROBE_SYMBOL(spurious_kernel_fault);
1043
1044int show_unhandled_signals = 1;
1045
1046static inline int
1047access_error(unsigned long error_code, struct vm_area_struct *vma)
1048{
1049 /* This is only called for the current mm, so: */
1050 bool foreign = false;
1051
1052 /*
1053 * Read or write was blocked by protection keys. This is
1054 * always an unconditional error and can never result in
1055 * a follow-up action to resolve the fault, like a COW.
1056 */
1057 if (error_code & X86_PF_PK)
1058 return 1;
1059
1060 /*
1061 * SGX hardware blocked the access. This usually happens
1062 * when the enclave memory contents have been destroyed, like
1063 * after a suspend/resume cycle. In any case, the kernel can't
1064 * fix the cause of the fault. Handle the fault as an access
1065 * error even in cases where no actual access violation
1066 * occurred. This allows userspace to rebuild the enclave in
1067 * response to the signal.
1068 */
1069 if (unlikely(error_code & X86_PF_SGX))
1070 return 1;
1071
1072 /*
1073 * Make sure to check the VMA so that we do not perform
1074 * faults just to hit a X86_PF_PK as soon as we fill in a
1075 * page.
1076 */
1077 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1078 (error_code & X86_PF_INSTR), foreign))
1079 return 1;
1080
1081 /*
1082 * Shadow stack accesses (PF_SHSTK=1) are only permitted to
1083 * shadow stack VMAs. All other accesses result in an error.
1084 */
1085 if (error_code & X86_PF_SHSTK) {
1086 if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK)))
1087 return 1;
1088 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1089 return 1;
1090 return 0;
1091 }
1092
1093 if (error_code & X86_PF_WRITE) {
1094 /* write, present and write, not present: */
1095 if (unlikely(vma->vm_flags & VM_SHADOW_STACK))
1096 return 1;
1097 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1098 return 1;
1099 return 0;
1100 }
1101
1102 /* read, present: */
1103 if (unlikely(error_code & X86_PF_PROT))
1104 return 1;
1105
1106 /* read, not present: */
1107 if (unlikely(!vma_is_accessible(vma)))
1108 return 1;
1109
1110 return 0;
1111}
1112
1113bool fault_in_kernel_space(unsigned long address)
1114{
1115 /*
1116 * On 64-bit systems, the vsyscall page is at an address above
1117 * TASK_SIZE_MAX, but is not considered part of the kernel
1118 * address space.
1119 */
1120 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1121 return false;
1122
1123 return address >= TASK_SIZE_MAX;
1124}
1125
1126/*
1127 * Called for all faults where 'address' is part of the kernel address
1128 * space. Might get called for faults that originate from *code* that
1129 * ran in userspace or the kernel.
1130 */
1131static void
1132do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1133 unsigned long address)
1134{
1135 /*
1136 * Protection keys exceptions only happen on user pages. We
1137 * have no user pages in the kernel portion of the address
1138 * space, so do not expect them here.
1139 */
1140 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1141
1142#ifdef CONFIG_X86_32
1143 /*
1144 * We can fault-in kernel-space virtual memory on-demand. The
1145 * 'reference' page table is init_mm.pgd.
1146 *
1147 * NOTE! We MUST NOT take any locks for this case. We may
1148 * be in an interrupt or a critical region, and should
1149 * only copy the information from the master page table,
1150 * nothing more.
1151 *
1152 * Before doing this on-demand faulting, ensure that the
1153 * fault is not any of the following:
1154 * 1. A fault on a PTE with a reserved bit set.
1155 * 2. A fault caused by a user-mode access. (Do not demand-
1156 * fault kernel memory due to user-mode accesses).
1157 * 3. A fault caused by a page-level protection violation.
1158 * (A demand fault would be on a non-present page which
1159 * would have X86_PF_PROT==0).
1160 *
1161 * This is only needed to close a race condition on x86-32 in
1162 * the vmalloc mapping/unmapping code. See the comment above
1163 * vmalloc_fault() for details. On x86-64 the race does not
1164 * exist as the vmalloc mappings don't need to be synchronized
1165 * there.
1166 */
1167 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1168 if (vmalloc_fault(address) >= 0)
1169 return;
1170 }
1171#endif
1172
1173 if (is_f00f_bug(regs, hw_error_code, address))
1174 return;
1175
1176 /* Was the fault spurious, caused by lazy TLB invalidation? */
1177 if (spurious_kernel_fault(hw_error_code, address))
1178 return;
1179
1180 /* kprobes don't want to hook the spurious faults: */
1181 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1182 return;
1183
1184 /*
1185 * Note, despite being a "bad area", there are quite a few
1186 * acceptable reasons to get here, such as erratum fixups
1187 * and handling kernel code that can fault, like get_user().
1188 *
1189 * Don't take the mm semaphore here. If we fixup a prefetch
1190 * fault we could otherwise deadlock:
1191 */
1192 bad_area_nosemaphore(regs, hw_error_code, address);
1193}
1194NOKPROBE_SYMBOL(do_kern_addr_fault);
1195
1196/*
1197 * Handle faults in the user portion of the address space. Nothing in here
1198 * should check X86_PF_USER without a specific justification: for almost
1199 * all purposes, we should treat a normal kernel access to user memory
1200 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1201 * The one exception is AC flag handling, which is, per the x86
1202 * architecture, special for WRUSS.
1203 */
1204static inline
1205void do_user_addr_fault(struct pt_regs *regs,
1206 unsigned long error_code,
1207 unsigned long address)
1208{
1209 struct vm_area_struct *vma;
1210 struct task_struct *tsk;
1211 struct mm_struct *mm;
1212 vm_fault_t fault;
1213 unsigned int flags = FAULT_FLAG_DEFAULT;
1214
1215 tsk = current;
1216 mm = tsk->mm;
1217
1218 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1219 /*
1220 * Whoops, this is kernel mode code trying to execute from
1221 * user memory. Unless this is AMD erratum #93, which
1222 * corrupts RIP such that it looks like a user address,
1223 * this is unrecoverable. Don't even try to look up the
1224 * VMA or look for extable entries.
1225 */
1226 if (is_errata93(regs, address))
1227 return;
1228
1229 page_fault_oops(regs, error_code, address);
1230 return;
1231 }
1232
1233 /* kprobes don't want to hook the spurious faults: */
1234 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1235 return;
1236
1237 /*
1238 * Reserved bits are never expected to be set on
1239 * entries in the user portion of the page tables.
1240 */
1241 if (unlikely(error_code & X86_PF_RSVD))
1242 pgtable_bad(regs, error_code, address);
1243
1244 /*
1245 * If SMAP is on, check for invalid kernel (supervisor) access to user
1246 * pages in the user address space. The odd case here is WRUSS,
1247 * which, according to the preliminary documentation, does not respect
1248 * SMAP and will have the USER bit set so, in all cases, SMAP
1249 * enforcement appears to be consistent with the USER bit.
1250 */
1251 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1252 !(error_code & X86_PF_USER) &&
1253 !(regs->flags & X86_EFLAGS_AC))) {
1254 /*
1255 * No extable entry here. This was a kernel access to an
1256 * invalid pointer. get_kernel_nofault() will not get here.
1257 */
1258 page_fault_oops(regs, error_code, address);
1259 return;
1260 }
1261
1262 /*
1263 * If we're in an interrupt, have no user context or are running
1264 * in a region with pagefaults disabled then we must not take the fault
1265 */
1266 if (unlikely(faulthandler_disabled() || !mm)) {
1267 bad_area_nosemaphore(regs, error_code, address);
1268 return;
1269 }
1270
1271 /* Legacy check - remove this after verifying that it doesn't trigger */
1272 if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) {
1273 bad_area_nosemaphore(regs, error_code, address);
1274 return;
1275 }
1276
1277 local_irq_enable();
1278
1279 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1280
1281 /*
1282 * Read-only permissions can not be expressed in shadow stack PTEs.
1283 * Treat all shadow stack accesses as WRITE faults. This ensures
1284 * that the MM will prepare everything (e.g., break COW) such that
1285 * maybe_mkwrite() can create a proper shadow stack PTE.
1286 */
1287 if (error_code & X86_PF_SHSTK)
1288 flags |= FAULT_FLAG_WRITE;
1289 if (error_code & X86_PF_WRITE)
1290 flags |= FAULT_FLAG_WRITE;
1291 if (error_code & X86_PF_INSTR)
1292 flags |= FAULT_FLAG_INSTRUCTION;
1293
1294 /*
1295 * We set FAULT_FLAG_USER based on the register state, not
1296 * based on X86_PF_USER. User space accesses that cause
1297 * system page faults are still user accesses.
1298 */
1299 if (user_mode(regs))
1300 flags |= FAULT_FLAG_USER;
1301
1302#ifdef CONFIG_X86_64
1303 /*
1304 * Faults in the vsyscall page might need emulation. The
1305 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1306 * considered to be part of the user address space.
1307 *
1308 * The vsyscall page does not have a "real" VMA, so do this
1309 * emulation before we go searching for VMAs.
1310 *
1311 * PKRU never rejects instruction fetches, so we don't need
1312 * to consider the PF_PK bit.
1313 */
1314 if (is_vsyscall_vaddr(address)) {
1315 if (emulate_vsyscall(error_code, regs, address))
1316 return;
1317 }
1318#endif
1319
1320 if (!(flags & FAULT_FLAG_USER))
1321 goto lock_mmap;
1322
1323 vma = lock_vma_under_rcu(mm, address);
1324 if (!vma)
1325 goto lock_mmap;
1326
1327 if (unlikely(access_error(error_code, vma))) {
1328 vma_end_read(vma);
1329 goto lock_mmap;
1330 }
1331 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
1332 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
1333 vma_end_read(vma);
1334
1335 if (!(fault & VM_FAULT_RETRY)) {
1336 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
1337 goto done;
1338 }
1339 count_vm_vma_lock_event(VMA_LOCK_RETRY);
1340 if (fault & VM_FAULT_MAJOR)
1341 flags |= FAULT_FLAG_TRIED;
1342
1343 /* Quick path to respond to signals */
1344 if (fault_signal_pending(fault, regs)) {
1345 if (!user_mode(regs))
1346 kernelmode_fixup_or_oops(regs, error_code, address,
1347 SIGBUS, BUS_ADRERR,
1348 ARCH_DEFAULT_PKEY);
1349 return;
1350 }
1351lock_mmap:
1352
1353retry:
1354 vma = lock_mm_and_find_vma(mm, address, regs);
1355 if (unlikely(!vma)) {
1356 bad_area_nosemaphore(regs, error_code, address);
1357 return;
1358 }
1359
1360 /*
1361 * Ok, we have a good vm_area for this memory access, so
1362 * we can handle it..
1363 */
1364 if (unlikely(access_error(error_code, vma))) {
1365 bad_area_access_error(regs, error_code, address, vma);
1366 return;
1367 }
1368
1369 /*
1370 * If for any reason at all we couldn't handle the fault,
1371 * make sure we exit gracefully rather than endlessly redo
1372 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1373 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1374 *
1375 * Note that handle_userfault() may also release and reacquire mmap_lock
1376 * (and not return with VM_FAULT_RETRY), when returning to userland to
1377 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1378 * (potentially after handling any pending signal during the return to
1379 * userland). The return to userland is identified whenever
1380 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1381 */
1382 fault = handle_mm_fault(vma, address, flags, regs);
1383
1384 if (fault_signal_pending(fault, regs)) {
1385 /*
1386 * Quick path to respond to signals. The core mm code
1387 * has unlocked the mm for us if we get here.
1388 */
1389 if (!user_mode(regs))
1390 kernelmode_fixup_or_oops(regs, error_code, address,
1391 SIGBUS, BUS_ADRERR,
1392 ARCH_DEFAULT_PKEY);
1393 return;
1394 }
1395
1396 /* The fault is fully completed (including releasing mmap lock) */
1397 if (fault & VM_FAULT_COMPLETED)
1398 return;
1399
1400 /*
1401 * If we need to retry the mmap_lock has already been released,
1402 * and if there is a fatal signal pending there is no guarantee
1403 * that we made any progress. Handle this case first.
1404 */
1405 if (unlikely(fault & VM_FAULT_RETRY)) {
1406 flags |= FAULT_FLAG_TRIED;
1407 goto retry;
1408 }
1409
1410 mmap_read_unlock(mm);
1411done:
1412 if (likely(!(fault & VM_FAULT_ERROR)))
1413 return;
1414
1415 if (fatal_signal_pending(current) && !user_mode(regs)) {
1416 kernelmode_fixup_or_oops(regs, error_code, address,
1417 0, 0, ARCH_DEFAULT_PKEY);
1418 return;
1419 }
1420
1421 if (fault & VM_FAULT_OOM) {
1422 /* Kernel mode? Handle exceptions or die: */
1423 if (!user_mode(regs)) {
1424 kernelmode_fixup_or_oops(regs, error_code, address,
1425 SIGSEGV, SEGV_MAPERR,
1426 ARCH_DEFAULT_PKEY);
1427 return;
1428 }
1429
1430 /*
1431 * We ran out of memory, call the OOM killer, and return the
1432 * userspace (which will retry the fault, or kill us if we got
1433 * oom-killed):
1434 */
1435 pagefault_out_of_memory();
1436 } else {
1437 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1438 VM_FAULT_HWPOISON_LARGE))
1439 do_sigbus(regs, error_code, address, fault);
1440 else if (fault & VM_FAULT_SIGSEGV)
1441 bad_area_nosemaphore(regs, error_code, address);
1442 else
1443 BUG();
1444 }
1445}
1446NOKPROBE_SYMBOL(do_user_addr_fault);
1447
1448static __always_inline void
1449trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1450 unsigned long address)
1451{
1452 if (!trace_pagefault_enabled())
1453 return;
1454
1455 if (user_mode(regs))
1456 trace_page_fault_user(address, regs, error_code);
1457 else
1458 trace_page_fault_kernel(address, regs, error_code);
1459}
1460
1461static __always_inline void
1462handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1463 unsigned long address)
1464{
1465 trace_page_fault_entries(regs, error_code, address);
1466
1467 if (unlikely(kmmio_fault(regs, address)))
1468 return;
1469
1470 /* Was the fault on kernel-controlled part of the address space? */
1471 if (unlikely(fault_in_kernel_space(address))) {
1472 do_kern_addr_fault(regs, error_code, address);
1473 } else {
1474 do_user_addr_fault(regs, error_code, address);
1475 /*
1476 * User address page fault handling might have reenabled
1477 * interrupts. Fixing up all potential exit points of
1478 * do_user_addr_fault() and its leaf functions is just not
1479 * doable w/o creating an unholy mess or turning the code
1480 * upside down.
1481 */
1482 local_irq_disable();
1483 }
1484}
1485
1486DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1487{
1488 irqentry_state_t state;
1489 unsigned long address;
1490
1491 address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2();
1492
1493 prefetchw(¤t->mm->mmap_lock);
1494
1495 /*
1496 * KVM uses #PF vector to deliver 'page not present' events to guests
1497 * (asynchronous page fault mechanism). The event happens when a
1498 * userspace task is trying to access some valid (from guest's point of
1499 * view) memory which is not currently mapped by the host (e.g. the
1500 * memory is swapped out). Note, the corresponding "page ready" event
1501 * which is injected when the memory becomes available, is delivered via
1502 * an interrupt mechanism and not a #PF exception
1503 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1504 *
1505 * We are relying on the interrupted context being sane (valid RSP,
1506 * relevant locks not held, etc.), which is fine as long as the
1507 * interrupted context had IF=1. We are also relying on the KVM
1508 * async pf type field and CR2 being read consistently instead of
1509 * getting values from real and async page faults mixed up.
1510 *
1511 * Fingers crossed.
1512 *
1513 * The async #PF handling code takes care of idtentry handling
1514 * itself.
1515 */
1516 if (kvm_handle_async_pf(regs, (u32)address))
1517 return;
1518
1519 /*
1520 * Entry handling for valid #PF from kernel mode is slightly
1521 * different: RCU is already watching and ct_irq_enter() must not
1522 * be invoked because a kernel fault on a user space address might
1523 * sleep.
1524 *
1525 * In case the fault hit a RCU idle region the conditional entry
1526 * code reenabled RCU to avoid subsequent wreckage which helps
1527 * debuggability.
1528 */
1529 state = irqentry_enter(regs);
1530
1531 instrumentation_begin();
1532 handle_page_fault(regs, error_code, address);
1533 instrumentation_end();
1534
1535 irqentry_exit(regs, state);
1536}