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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#include <linux/mm.h> /* find_and_lock_vma() */
23#include <linux/vmalloc.h>
24
25#include <asm/cpufeature.h> /* boot_cpu_has, ... */
26#include <asm/traps.h> /* dotraplinkage, ... */
27#include <asm/fixmap.h> /* VSYSCALL_ADDR */
28#include <asm/vsyscall.h> /* emulate_vsyscall */
29#include <asm/vm86.h> /* struct vm86 */
30#include <asm/mmu_context.h> /* vma_pkey() */
31#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
32#include <asm/desc.h> /* store_idt(), ... */
33#include <asm/cpu_entry_area.h> /* exception stack */
34#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
35#include <asm/kvm_para.h> /* kvm_handle_async_pf */
36#include <asm/vdso.h> /* fixup_vdso_exception() */
37#include <asm/irq_stack.h>
38#include <asm/fred.h>
39#include <asm/sev.h> /* snp_dump_hva_rmpentry() */
40
41#define CREATE_TRACE_POINTS
42#include <asm/trace/exceptions.h>
43
44/*
45 * Returns 0 if mmiotrace is disabled, or if the fault is not
46 * handled by mmiotrace:
47 */
48static nokprobe_inline int
49kmmio_fault(struct pt_regs *regs, unsigned long addr)
50{
51 if (unlikely(is_kmmio_active()))
52 if (kmmio_handler(regs, addr) == 1)
53 return -1;
54 return 0;
55}
56
57/*
58 * Prefetch quirks:
59 *
60 * 32-bit mode:
61 *
62 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
63 * Check that here and ignore it. This is AMD erratum #91.
64 *
65 * 64-bit mode:
66 *
67 * Sometimes the CPU reports invalid exceptions on prefetch.
68 * Check that here and ignore it.
69 *
70 * Opcode checker based on code by Richard Brunner.
71 */
72static inline int
73check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
74 unsigned char opcode, int *prefetch)
75{
76 unsigned char instr_hi = opcode & 0xf0;
77 unsigned char instr_lo = opcode & 0x0f;
78
79 switch (instr_hi) {
80 case 0x20:
81 case 0x30:
82 /*
83 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
84 * In X86_64 long mode, the CPU will signal invalid
85 * opcode if some of these prefixes are present so
86 * X86_64 will never get here anyway
87 */
88 return ((instr_lo & 7) == 0x6);
89#ifdef CONFIG_X86_64
90 case 0x40:
91 /*
92 * In 64-bit mode 0x40..0x4F are valid REX prefixes
93 */
94 return (!user_mode(regs) || user_64bit_mode(regs));
95#endif
96 case 0x60:
97 /* 0x64 thru 0x67 are valid prefixes in all modes. */
98 return (instr_lo & 0xC) == 0x4;
99 case 0xF0:
100 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
101 return !instr_lo || (instr_lo>>1) == 1;
102 case 0x00:
103 /* Prefetch instruction is 0x0F0D or 0x0F18 */
104 if (get_kernel_nofault(opcode, instr))
105 return 0;
106
107 *prefetch = (instr_lo == 0xF) &&
108 (opcode == 0x0D || opcode == 0x18);
109 return 0;
110 default:
111 return 0;
112 }
113}
114
115static bool is_amd_k8_pre_npt(void)
116{
117 struct cpuinfo_x86 *c = &boot_cpu_data;
118
119 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
120 c->x86_vendor == X86_VENDOR_AMD &&
121 c->x86 == 0xf && c->x86_model < 0x40);
122}
123
124static int
125is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
126{
127 unsigned char *max_instr;
128 unsigned char *instr;
129 int prefetch = 0;
130
131 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
132 if (!is_amd_k8_pre_npt())
133 return 0;
134
135 /*
136 * If it was a exec (instruction fetch) fault on NX page, then
137 * do not ignore the fault:
138 */
139 if (error_code & X86_PF_INSTR)
140 return 0;
141
142 instr = (void *)convert_ip_to_linear(current, regs);
143 max_instr = instr + 15;
144
145 /*
146 * This code has historically always bailed out if IP points to a
147 * not-present page (e.g. due to a race). No one has ever
148 * complained about this.
149 */
150 pagefault_disable();
151
152 while (instr < max_instr) {
153 unsigned char opcode;
154
155 if (user_mode(regs)) {
156 if (get_user(opcode, (unsigned char __user *) instr))
157 break;
158 } else {
159 if (get_kernel_nofault(opcode, instr))
160 break;
161 }
162
163 instr++;
164
165 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
166 break;
167 }
168
169 pagefault_enable();
170 return prefetch;
171}
172
173DEFINE_SPINLOCK(pgd_lock);
174LIST_HEAD(pgd_list);
175
176#ifdef CONFIG_X86_32
177static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
178{
179 unsigned index = pgd_index(address);
180 pgd_t *pgd_k;
181 p4d_t *p4d, *p4d_k;
182 pud_t *pud, *pud_k;
183 pmd_t *pmd, *pmd_k;
184
185 pgd += index;
186 pgd_k = init_mm.pgd + index;
187
188 if (!pgd_present(*pgd_k))
189 return NULL;
190
191 /*
192 * set_pgd(pgd, *pgd_k); here would be useless on PAE
193 * and redundant with the set_pmd() on non-PAE. As would
194 * set_p4d/set_pud.
195 */
196 p4d = p4d_offset(pgd, address);
197 p4d_k = p4d_offset(pgd_k, address);
198 if (!p4d_present(*p4d_k))
199 return NULL;
200
201 pud = pud_offset(p4d, address);
202 pud_k = pud_offset(p4d_k, address);
203 if (!pud_present(*pud_k))
204 return NULL;
205
206 pmd = pmd_offset(pud, address);
207 pmd_k = pmd_offset(pud_k, address);
208
209 if (pmd_present(*pmd) != pmd_present(*pmd_k))
210 set_pmd(pmd, *pmd_k);
211
212 if (!pmd_present(*pmd_k))
213 return NULL;
214 else
215 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
216
217 return pmd_k;
218}
219
220/*
221 * Handle a fault on the vmalloc or module mapping area
222 *
223 * This is needed because there is a race condition between the time
224 * when the vmalloc mapping code updates the PMD to the point in time
225 * where it synchronizes this update with the other page-tables in the
226 * system.
227 *
228 * In this race window another thread/CPU can map an area on the same
229 * PMD, finds it already present and does not synchronize it with the
230 * rest of the system yet. As a result v[mz]alloc might return areas
231 * which are not mapped in every page-table in the system, causing an
232 * unhandled page-fault when they are accessed.
233 */
234static noinline int vmalloc_fault(unsigned long address)
235{
236 unsigned long pgd_paddr;
237 pmd_t *pmd_k;
238 pte_t *pte_k;
239
240 /* Make sure we are in vmalloc area: */
241 if (!(address >= VMALLOC_START && address < VMALLOC_END))
242 return -1;
243
244 /*
245 * Synchronize this task's top level page-table
246 * with the 'reference' page table.
247 *
248 * Do _not_ use "current" here. We might be inside
249 * an interrupt in the middle of a task switch..
250 */
251 pgd_paddr = read_cr3_pa();
252 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
253 if (!pmd_k)
254 return -1;
255
256 if (pmd_leaf(*pmd_k))
257 return 0;
258
259 pte_k = pte_offset_kernel(pmd_k, address);
260 if (!pte_present(*pte_k))
261 return -1;
262
263 return 0;
264}
265NOKPROBE_SYMBOL(vmalloc_fault);
266
267void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
268{
269 unsigned long addr;
270
271 for (addr = start & PMD_MASK;
272 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
273 addr += PMD_SIZE) {
274 struct page *page;
275
276 spin_lock(&pgd_lock);
277 list_for_each_entry(page, &pgd_list, lru) {
278 spinlock_t *pgt_lock;
279
280 /* the pgt_lock only for Xen */
281 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
282
283 spin_lock(pgt_lock);
284 vmalloc_sync_one(page_address(page), addr);
285 spin_unlock(pgt_lock);
286 }
287 spin_unlock(&pgd_lock);
288 }
289}
290
291static bool low_pfn(unsigned long pfn)
292{
293 return pfn < max_low_pfn;
294}
295
296static void dump_pagetable(unsigned long address)
297{
298 pgd_t *base = __va(read_cr3_pa());
299 pgd_t *pgd = &base[pgd_index(address)];
300 p4d_t *p4d;
301 pud_t *pud;
302 pmd_t *pmd;
303 pte_t *pte;
304
305#ifdef CONFIG_X86_PAE
306 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
307 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
308 goto out;
309#define pr_pde pr_cont
310#else
311#define pr_pde pr_info
312#endif
313 p4d = p4d_offset(pgd, address);
314 pud = pud_offset(p4d, address);
315 pmd = pmd_offset(pud, address);
316 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
317#undef pr_pde
318
319 /*
320 * We must not directly access the pte in the highpte
321 * case if the page table is located in highmem.
322 * And let's rather not kmap-atomic the pte, just in case
323 * it's allocated already:
324 */
325 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_leaf(*pmd))
326 goto out;
327
328 pte = pte_offset_kernel(pmd, address);
329 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
330out:
331 pr_cont("\n");
332}
333
334#else /* CONFIG_X86_64: */
335
336#ifdef CONFIG_CPU_SUP_AMD
337static const char errata93_warning[] =
338KERN_ERR
339"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
340"******* Working around it, but it may cause SEGVs or burn power.\n"
341"******* Please consider a BIOS update.\n"
342"******* Disabling USB legacy in the BIOS may also help.\n";
343#endif
344
345static int bad_address(void *p)
346{
347 unsigned long dummy;
348
349 return get_kernel_nofault(dummy, (unsigned long *)p);
350}
351
352static void dump_pagetable(unsigned long address)
353{
354 pgd_t *base = __va(read_cr3_pa());
355 pgd_t *pgd = base + pgd_index(address);
356 p4d_t *p4d;
357 pud_t *pud;
358 pmd_t *pmd;
359 pte_t *pte;
360
361 if (bad_address(pgd))
362 goto bad;
363
364 pr_info("PGD %lx ", pgd_val(*pgd));
365
366 if (!pgd_present(*pgd))
367 goto out;
368
369 p4d = p4d_offset(pgd, address);
370 if (bad_address(p4d))
371 goto bad;
372
373 pr_cont("P4D %lx ", p4d_val(*p4d));
374 if (!p4d_present(*p4d) || p4d_leaf(*p4d))
375 goto out;
376
377 pud = pud_offset(p4d, address);
378 if (bad_address(pud))
379 goto bad;
380
381 pr_cont("PUD %lx ", pud_val(*pud));
382 if (!pud_present(*pud) || pud_leaf(*pud))
383 goto out;
384
385 pmd = pmd_offset(pud, address);
386 if (bad_address(pmd))
387 goto bad;
388
389 pr_cont("PMD %lx ", pmd_val(*pmd));
390 if (!pmd_present(*pmd) || pmd_leaf(*pmd))
391 goto out;
392
393 pte = pte_offset_kernel(pmd, address);
394 if (bad_address(pte))
395 goto bad;
396
397 pr_cont("PTE %lx", pte_val(*pte));
398out:
399 pr_cont("\n");
400 return;
401bad:
402 pr_info("BAD\n");
403}
404
405#endif /* CONFIG_X86_64 */
406
407/*
408 * Workaround for K8 erratum #93 & buggy BIOS.
409 *
410 * BIOS SMM functions are required to use a specific workaround
411 * to avoid corruption of the 64bit RIP register on C stepping K8.
412 *
413 * A lot of BIOS that didn't get tested properly miss this.
414 *
415 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
416 * Try to work around it here.
417 *
418 * Note we only handle faults in kernel here.
419 * Does nothing on 32-bit.
420 */
421static int is_errata93(struct pt_regs *regs, unsigned long address)
422{
423#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
424 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
425 || boot_cpu_data.x86 != 0xf)
426 return 0;
427
428 if (user_mode(regs))
429 return 0;
430
431 if (address != regs->ip)
432 return 0;
433
434 if ((address >> 32) != 0)
435 return 0;
436
437 address |= 0xffffffffUL << 32;
438 if ((address >= (u64)_stext && address <= (u64)_etext) ||
439 (address >= MODULES_VADDR && address <= MODULES_END)) {
440 printk_once(errata93_warning);
441 regs->ip = address;
442 return 1;
443 }
444#endif
445 return 0;
446}
447
448/*
449 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
450 * to illegal addresses >4GB.
451 *
452 * We catch this in the page fault handler because these addresses
453 * are not reachable. Just detect this case and return. Any code
454 * segment in LDT is compatibility mode.
455 */
456static int is_errata100(struct pt_regs *regs, unsigned long address)
457{
458#ifdef CONFIG_X86_64
459 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
460 return 1;
461#endif
462 return 0;
463}
464
465/* Pentium F0 0F C7 C8 bug workaround: */
466static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
467 unsigned long address)
468{
469#ifdef CONFIG_X86_F00F_BUG
470 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
471 idt_is_f00f_address(address)) {
472 handle_invalid_op(regs);
473 return 1;
474 }
475#endif
476 return 0;
477}
478
479static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
480{
481 u32 offset = (index >> 3) * sizeof(struct desc_struct);
482 unsigned long addr;
483 struct ldttss_desc desc;
484
485 if (index == 0) {
486 pr_alert("%s: NULL\n", name);
487 return;
488 }
489
490 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
491 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
492 return;
493 }
494
495 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
496 sizeof(struct ldttss_desc))) {
497 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
498 name, index);
499 return;
500 }
501
502 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
503#ifdef CONFIG_X86_64
504 addr |= ((u64)desc.base3 << 32);
505#endif
506 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
507 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
508}
509
510static void
511show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
512{
513 if (!oops_may_print())
514 return;
515
516 if (error_code & X86_PF_INSTR) {
517 unsigned int level;
518 bool nx, rw;
519 pgd_t *pgd;
520 pte_t *pte;
521
522 pgd = __va(read_cr3_pa());
523 pgd += pgd_index(address);
524
525 pte = lookup_address_in_pgd_attr(pgd, address, &level, &nx, &rw);
526
527 if (pte && pte_present(*pte) && (!pte_exec(*pte) || nx))
528 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
529 from_kuid(&init_user_ns, current_uid()));
530 if (pte && pte_present(*pte) && pte_exec(*pte) && !nx &&
531 (pgd_flags(*pgd) & _PAGE_USER) &&
532 (__read_cr4() & X86_CR4_SMEP))
533 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
534 from_kuid(&init_user_ns, current_uid()));
535 }
536
537 if (address < PAGE_SIZE && !user_mode(regs))
538 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
539 (void *)address);
540 else
541 pr_alert("BUG: unable to handle page fault for address: %px\n",
542 (void *)address);
543
544 pr_alert("#PF: %s %s in %s mode\n",
545 (error_code & X86_PF_USER) ? "user" : "supervisor",
546 (error_code & X86_PF_INSTR) ? "instruction fetch" :
547 (error_code & X86_PF_WRITE) ? "write access" :
548 "read access",
549 user_mode(regs) ? "user" : "kernel");
550 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
551 !(error_code & X86_PF_PROT) ? "not-present page" :
552 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
553 (error_code & X86_PF_PK) ? "protection keys violation" :
554 (error_code & X86_PF_RMP) ? "RMP violation" :
555 "permissions violation");
556
557 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
558 struct desc_ptr idt, gdt;
559 u16 ldtr, tr;
560
561 /*
562 * This can happen for quite a few reasons. The more obvious
563 * ones are faults accessing the GDT, or LDT. Perhaps
564 * surprisingly, if the CPU tries to deliver a benign or
565 * contributory exception from user code and gets a page fault
566 * during delivery, the page fault can be delivered as though
567 * it originated directly from user code. This could happen
568 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
569 * kernel or IST stack.
570 */
571 store_idt(&idt);
572
573 /* Usable even on Xen PV -- it's just slow. */
574 native_store_gdt(&gdt);
575
576 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
577 idt.address, idt.size, gdt.address, gdt.size);
578
579 store_ldt(ldtr);
580 show_ldttss(&gdt, "LDTR", ldtr);
581
582 store_tr(tr);
583 show_ldttss(&gdt, "TR", tr);
584 }
585
586 dump_pagetable(address);
587
588 if (error_code & X86_PF_RMP)
589 snp_dump_hva_rmpentry(address);
590}
591
592static noinline void
593pgtable_bad(struct pt_regs *regs, unsigned long error_code,
594 unsigned long address)
595{
596 struct task_struct *tsk;
597 unsigned long flags;
598 int sig;
599
600 flags = oops_begin();
601 tsk = current;
602 sig = SIGKILL;
603
604 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
605 tsk->comm, address);
606 dump_pagetable(address);
607
608 if (__die("Bad pagetable", regs, error_code))
609 sig = 0;
610
611 oops_end(flags, regs, sig);
612}
613
614static void sanitize_error_code(unsigned long address,
615 unsigned long *error_code)
616{
617 /*
618 * To avoid leaking information about the kernel page
619 * table layout, pretend that user-mode accesses to
620 * kernel addresses are always protection faults.
621 *
622 * NB: This means that failed vsyscalls with vsyscall=none
623 * will have the PROT bit. This doesn't leak any
624 * information and does not appear to cause any problems.
625 */
626 if (address >= TASK_SIZE_MAX)
627 *error_code |= X86_PF_PROT;
628}
629
630static void set_signal_archinfo(unsigned long address,
631 unsigned long error_code)
632{
633 struct task_struct *tsk = current;
634
635 tsk->thread.trap_nr = X86_TRAP_PF;
636 tsk->thread.error_code = error_code | X86_PF_USER;
637 tsk->thread.cr2 = address;
638}
639
640static noinline void
641page_fault_oops(struct pt_regs *regs, unsigned long error_code,
642 unsigned long address)
643{
644#ifdef CONFIG_VMAP_STACK
645 struct stack_info info;
646#endif
647 unsigned long flags;
648 int sig;
649
650 if (user_mode(regs)) {
651 /*
652 * Implicit kernel access from user mode? Skip the stack
653 * overflow and EFI special cases.
654 */
655 goto oops;
656 }
657
658#ifdef CONFIG_VMAP_STACK
659 /*
660 * Stack overflow? During boot, we can fault near the initial
661 * stack in the direct map, but that's not an overflow -- check
662 * that we're in vmalloc space to avoid this.
663 */
664 if (is_vmalloc_addr((void *)address) &&
665 get_stack_guard_info((void *)address, &info)) {
666 /*
667 * We're likely to be running with very little stack space
668 * left. It's plausible that we'd hit this condition but
669 * double-fault even before we get this far, in which case
670 * we're fine: the double-fault handler will deal with it.
671 *
672 * We don't want to make it all the way into the oops code
673 * and then double-fault, though, because we're likely to
674 * break the console driver and lose most of the stack dump.
675 */
676 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
677 handle_stack_overflow,
678 ASM_CALL_ARG3,
679 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
680
681 BUG();
682 }
683#endif
684
685 /*
686 * Buggy firmware could access regions which might page fault. If
687 * this happens, EFI has a special OOPS path that will try to
688 * avoid hanging the system.
689 */
690 if (IS_ENABLED(CONFIG_EFI))
691 efi_crash_gracefully_on_page_fault(address);
692
693 /* Only not-present faults should be handled by KFENCE. */
694 if (!(error_code & X86_PF_PROT) &&
695 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
696 return;
697
698oops:
699 /*
700 * Oops. The kernel tried to access some bad page. We'll have to
701 * terminate things with extreme prejudice:
702 */
703 flags = oops_begin();
704
705 show_fault_oops(regs, error_code, address);
706
707 if (task_stack_end_corrupted(current))
708 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
709
710 sig = SIGKILL;
711 if (__die("Oops", regs, error_code))
712 sig = 0;
713
714 /* Executive summary in case the body of the oops scrolled away */
715 printk(KERN_DEFAULT "CR2: %016lx\n", address);
716
717 oops_end(flags, regs, sig);
718}
719
720static noinline void
721kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
722 unsigned long address, int signal, int si_code,
723 u32 pkey)
724{
725 WARN_ON_ONCE(user_mode(regs));
726
727 /* Are we prepared to handle this kernel fault? */
728 if (fixup_exception(regs, X86_TRAP_PF, error_code, address))
729 return;
730
731 /*
732 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
733 * instruction.
734 */
735 if (is_prefetch(regs, error_code, address))
736 return;
737
738 page_fault_oops(regs, error_code, address);
739}
740
741/*
742 * Print out info about fatal segfaults, if the show_unhandled_signals
743 * sysctl is set:
744 */
745static inline void
746show_signal_msg(struct pt_regs *regs, unsigned long error_code,
747 unsigned long address, struct task_struct *tsk)
748{
749 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
750 /* This is a racy snapshot, but it's better than nothing. */
751 int cpu = raw_smp_processor_id();
752
753 if (!unhandled_signal(tsk, SIGSEGV))
754 return;
755
756 if (!printk_ratelimit())
757 return;
758
759 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
760 loglvl, tsk->comm, task_pid_nr(tsk), address,
761 (void *)regs->ip, (void *)regs->sp, error_code);
762
763 print_vma_addr(KERN_CONT " in ", regs->ip);
764
765 /*
766 * Dump the likely CPU where the fatal segfault happened.
767 * This can help identify faulty hardware.
768 */
769 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
770 topology_core_id(cpu), topology_physical_package_id(cpu));
771
772
773 printk(KERN_CONT "\n");
774
775 show_opcodes(regs, loglvl);
776}
777
778static void
779__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
780 unsigned long address, u32 pkey, int si_code)
781{
782 struct task_struct *tsk = current;
783
784 if (!user_mode(regs)) {
785 kernelmode_fixup_or_oops(regs, error_code, address,
786 SIGSEGV, si_code, pkey);
787 return;
788 }
789
790 if (!(error_code & X86_PF_USER)) {
791 /* Implicit user access to kernel memory -- just oops */
792 page_fault_oops(regs, error_code, address);
793 return;
794 }
795
796 /*
797 * User mode accesses just cause a SIGSEGV.
798 * It's possible to have interrupts off here:
799 */
800 local_irq_enable();
801
802 /*
803 * Valid to do another page fault here because this one came
804 * from user space:
805 */
806 if (is_prefetch(regs, error_code, address))
807 return;
808
809 if (is_errata100(regs, address))
810 return;
811
812 sanitize_error_code(address, &error_code);
813
814 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
815 return;
816
817 if (likely(show_unhandled_signals))
818 show_signal_msg(regs, error_code, address, tsk);
819
820 set_signal_archinfo(address, error_code);
821
822 if (si_code == SEGV_PKUERR)
823 force_sig_pkuerr((void __user *)address, pkey);
824 else
825 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
826
827 local_irq_disable();
828}
829
830static noinline void
831bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
832 unsigned long address)
833{
834 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
835}
836
837static void
838__bad_area(struct pt_regs *regs, unsigned long error_code,
839 unsigned long address, struct mm_struct *mm,
840 struct vm_area_struct *vma, u32 pkey, int si_code)
841{
842 /*
843 * Something tried to access memory that isn't in our memory map..
844 * Fix it, but check if it's kernel or user first..
845 */
846 if (mm)
847 mmap_read_unlock(mm);
848 else
849 vma_end_read(vma);
850
851 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
852}
853
854static inline bool bad_area_access_from_pkeys(unsigned long error_code,
855 struct vm_area_struct *vma)
856{
857 /* This code is always called on the current mm */
858 bool foreign = false;
859
860 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
861 return false;
862 if (error_code & X86_PF_PK)
863 return true;
864 /* this checks permission keys on the VMA: */
865 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
866 (error_code & X86_PF_INSTR), foreign))
867 return true;
868 return false;
869}
870
871static noinline void
872bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
873 unsigned long address, struct mm_struct *mm,
874 struct vm_area_struct *vma)
875{
876 /*
877 * This OSPKE check is not strictly necessary at runtime.
878 * But, doing it this way allows compiler optimizations
879 * if pkeys are compiled out.
880 */
881 if (bad_area_access_from_pkeys(error_code, vma)) {
882 /*
883 * A protection key fault means that the PKRU value did not allow
884 * access to some PTE. Userspace can figure out what PKRU was
885 * from the XSAVE state. This function captures the pkey from
886 * the vma and passes it to userspace so userspace can discover
887 * which protection key was set on the PTE.
888 *
889 * If we get here, we know that the hardware signaled a X86_PF_PK
890 * fault and that there was a VMA once we got in the fault
891 * handler. It does *not* guarantee that the VMA we find here
892 * was the one that we faulted on.
893 *
894 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
895 * 2. T1 : set PKRU to deny access to pkey=4, touches page
896 * 3. T1 : faults...
897 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
898 * 5. T1 : enters fault handler, takes mmap_lock, etc...
899 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
900 * faulted on a pte with its pkey=4.
901 */
902 u32 pkey = vma_pkey(vma);
903
904 __bad_area(regs, error_code, address, mm, vma, pkey, SEGV_PKUERR);
905 } else {
906 __bad_area(regs, error_code, address, mm, vma, 0, SEGV_ACCERR);
907 }
908}
909
910static void
911do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
912 vm_fault_t fault)
913{
914 /* Kernel mode? Handle exceptions or die: */
915 if (!user_mode(regs)) {
916 kernelmode_fixup_or_oops(regs, error_code, address,
917 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
918 return;
919 }
920
921 /* User-space => ok to do another page fault: */
922 if (is_prefetch(regs, error_code, address))
923 return;
924
925 sanitize_error_code(address, &error_code);
926
927 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
928 return;
929
930 set_signal_archinfo(address, error_code);
931
932#ifdef CONFIG_MEMORY_FAILURE
933 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
934 struct task_struct *tsk = current;
935 unsigned lsb = 0;
936
937 pr_err(
938 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
939 tsk->comm, tsk->pid, address);
940 if (fault & VM_FAULT_HWPOISON_LARGE)
941 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
942 if (fault & VM_FAULT_HWPOISON)
943 lsb = PAGE_SHIFT;
944 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
945 return;
946 }
947#endif
948 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
949}
950
951static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
952{
953 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
954 return 0;
955
956 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
957 return 0;
958
959 return 1;
960}
961
962/*
963 * Handle a spurious fault caused by a stale TLB entry.
964 *
965 * This allows us to lazily refresh the TLB when increasing the
966 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
967 * eagerly is very expensive since that implies doing a full
968 * cross-processor TLB flush, even if no stale TLB entries exist
969 * on other processors.
970 *
971 * Spurious faults may only occur if the TLB contains an entry with
972 * fewer permission than the page table entry. Non-present (P = 0)
973 * and reserved bit (R = 1) faults are never spurious.
974 *
975 * There are no security implications to leaving a stale TLB when
976 * increasing the permissions on a page.
977 *
978 * Returns non-zero if a spurious fault was handled, zero otherwise.
979 *
980 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
981 * (Optional Invalidation).
982 */
983static noinline int
984spurious_kernel_fault(unsigned long error_code, unsigned long address)
985{
986 pgd_t *pgd;
987 p4d_t *p4d;
988 pud_t *pud;
989 pmd_t *pmd;
990 pte_t *pte;
991 int ret;
992
993 /*
994 * Only writes to RO or instruction fetches from NX may cause
995 * spurious faults.
996 *
997 * These could be from user or supervisor accesses but the TLB
998 * is only lazily flushed after a kernel mapping protection
999 * change, so user accesses are not expected to cause spurious
1000 * faults.
1001 */
1002 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1003 error_code != (X86_PF_INSTR | X86_PF_PROT))
1004 return 0;
1005
1006 pgd = init_mm.pgd + pgd_index(address);
1007 if (!pgd_present(*pgd))
1008 return 0;
1009
1010 p4d = p4d_offset(pgd, address);
1011 if (!p4d_present(*p4d))
1012 return 0;
1013
1014 if (p4d_leaf(*p4d))
1015 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1016
1017 pud = pud_offset(p4d, address);
1018 if (!pud_present(*pud))
1019 return 0;
1020
1021 if (pud_leaf(*pud))
1022 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1023
1024 pmd = pmd_offset(pud, address);
1025 if (!pmd_present(*pmd))
1026 return 0;
1027
1028 if (pmd_leaf(*pmd))
1029 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1030
1031 pte = pte_offset_kernel(pmd, address);
1032 if (!pte_present(*pte))
1033 return 0;
1034
1035 ret = spurious_kernel_fault_check(error_code, pte);
1036 if (!ret)
1037 return 0;
1038
1039 /*
1040 * Make sure we have permissions in PMD.
1041 * If not, then there's a bug in the page tables:
1042 */
1043 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1044 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1045
1046 return ret;
1047}
1048NOKPROBE_SYMBOL(spurious_kernel_fault);
1049
1050int show_unhandled_signals = 1;
1051
1052static inline int
1053access_error(unsigned long error_code, struct vm_area_struct *vma)
1054{
1055 /* This is only called for the current mm, so: */
1056 bool foreign = false;
1057
1058 /*
1059 * Read or write was blocked by protection keys. This is
1060 * always an unconditional error and can never result in
1061 * a follow-up action to resolve the fault, like a COW.
1062 */
1063 if (error_code & X86_PF_PK)
1064 return 1;
1065
1066 /*
1067 * SGX hardware blocked the access. This usually happens
1068 * when the enclave memory contents have been destroyed, like
1069 * after a suspend/resume cycle. In any case, the kernel can't
1070 * fix the cause of the fault. Handle the fault as an access
1071 * error even in cases where no actual access violation
1072 * occurred. This allows userspace to rebuild the enclave in
1073 * response to the signal.
1074 */
1075 if (unlikely(error_code & X86_PF_SGX))
1076 return 1;
1077
1078 /*
1079 * Make sure to check the VMA so that we do not perform
1080 * faults just to hit a X86_PF_PK as soon as we fill in a
1081 * page.
1082 */
1083 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1084 (error_code & X86_PF_INSTR), foreign))
1085 return 1;
1086
1087 /*
1088 * Shadow stack accesses (PF_SHSTK=1) are only permitted to
1089 * shadow stack VMAs. All other accesses result in an error.
1090 */
1091 if (error_code & X86_PF_SHSTK) {
1092 if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK)))
1093 return 1;
1094 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1095 return 1;
1096 return 0;
1097 }
1098
1099 if (error_code & X86_PF_WRITE) {
1100 /* write, present and write, not present: */
1101 if (unlikely(vma->vm_flags & VM_SHADOW_STACK))
1102 return 1;
1103 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1104 return 1;
1105 return 0;
1106 }
1107
1108 /* read, present: */
1109 if (unlikely(error_code & X86_PF_PROT))
1110 return 1;
1111
1112 /* read, not present: */
1113 if (unlikely(!vma_is_accessible(vma)))
1114 return 1;
1115
1116 return 0;
1117}
1118
1119bool fault_in_kernel_space(unsigned long address)
1120{
1121 /*
1122 * On 64-bit systems, the vsyscall page is at an address above
1123 * TASK_SIZE_MAX, but is not considered part of the kernel
1124 * address space.
1125 */
1126 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1127 return false;
1128
1129 return address >= TASK_SIZE_MAX;
1130}
1131
1132/*
1133 * Called for all faults where 'address' is part of the kernel address
1134 * space. Might get called for faults that originate from *code* that
1135 * ran in userspace or the kernel.
1136 */
1137static void
1138do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1139 unsigned long address)
1140{
1141 /*
1142 * Protection keys exceptions only happen on user pages. We
1143 * have no user pages in the kernel portion of the address
1144 * space, so do not expect them here.
1145 */
1146 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1147
1148#ifdef CONFIG_X86_32
1149 /*
1150 * We can fault-in kernel-space virtual memory on-demand. The
1151 * 'reference' page table is init_mm.pgd.
1152 *
1153 * NOTE! We MUST NOT take any locks for this case. We may
1154 * be in an interrupt or a critical region, and should
1155 * only copy the information from the master page table,
1156 * nothing more.
1157 *
1158 * Before doing this on-demand faulting, ensure that the
1159 * fault is not any of the following:
1160 * 1. A fault on a PTE with a reserved bit set.
1161 * 2. A fault caused by a user-mode access. (Do not demand-
1162 * fault kernel memory due to user-mode accesses).
1163 * 3. A fault caused by a page-level protection violation.
1164 * (A demand fault would be on a non-present page which
1165 * would have X86_PF_PROT==0).
1166 *
1167 * This is only needed to close a race condition on x86-32 in
1168 * the vmalloc mapping/unmapping code. See the comment above
1169 * vmalloc_fault() for details. On x86-64 the race does not
1170 * exist as the vmalloc mappings don't need to be synchronized
1171 * there.
1172 */
1173 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1174 if (vmalloc_fault(address) >= 0)
1175 return;
1176 }
1177#endif
1178
1179 if (is_f00f_bug(regs, hw_error_code, address))
1180 return;
1181
1182 /* Was the fault spurious, caused by lazy TLB invalidation? */
1183 if (spurious_kernel_fault(hw_error_code, address))
1184 return;
1185
1186 /* kprobes don't want to hook the spurious faults: */
1187 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1188 return;
1189
1190 /*
1191 * Note, despite being a "bad area", there are quite a few
1192 * acceptable reasons to get here, such as erratum fixups
1193 * and handling kernel code that can fault, like get_user().
1194 *
1195 * Don't take the mm semaphore here. If we fixup a prefetch
1196 * fault we could otherwise deadlock:
1197 */
1198 bad_area_nosemaphore(regs, hw_error_code, address);
1199}
1200NOKPROBE_SYMBOL(do_kern_addr_fault);
1201
1202/*
1203 * Handle faults in the user portion of the address space. Nothing in here
1204 * should check X86_PF_USER without a specific justification: for almost
1205 * all purposes, we should treat a normal kernel access to user memory
1206 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1207 * The one exception is AC flag handling, which is, per the x86
1208 * architecture, special for WRUSS.
1209 */
1210static inline
1211void do_user_addr_fault(struct pt_regs *regs,
1212 unsigned long error_code,
1213 unsigned long address)
1214{
1215 struct vm_area_struct *vma;
1216 struct task_struct *tsk;
1217 struct mm_struct *mm;
1218 vm_fault_t fault;
1219 unsigned int flags = FAULT_FLAG_DEFAULT;
1220
1221 tsk = current;
1222 mm = tsk->mm;
1223
1224 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1225 /*
1226 * Whoops, this is kernel mode code trying to execute from
1227 * user memory. Unless this is AMD erratum #93, which
1228 * corrupts RIP such that it looks like a user address,
1229 * this is unrecoverable. Don't even try to look up the
1230 * VMA or look for extable entries.
1231 */
1232 if (is_errata93(regs, address))
1233 return;
1234
1235 page_fault_oops(regs, error_code, address);
1236 return;
1237 }
1238
1239 /* kprobes don't want to hook the spurious faults: */
1240 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1241 return;
1242
1243 /*
1244 * Reserved bits are never expected to be set on
1245 * entries in the user portion of the page tables.
1246 */
1247 if (unlikely(error_code & X86_PF_RSVD))
1248 pgtable_bad(regs, error_code, address);
1249
1250 /*
1251 * If SMAP is on, check for invalid kernel (supervisor) access to user
1252 * pages in the user address space. The odd case here is WRUSS,
1253 * which, according to the preliminary documentation, does not respect
1254 * SMAP and will have the USER bit set so, in all cases, SMAP
1255 * enforcement appears to be consistent with the USER bit.
1256 */
1257 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1258 !(error_code & X86_PF_USER) &&
1259 !(regs->flags & X86_EFLAGS_AC))) {
1260 /*
1261 * No extable entry here. This was a kernel access to an
1262 * invalid pointer. get_kernel_nofault() will not get here.
1263 */
1264 page_fault_oops(regs, error_code, address);
1265 return;
1266 }
1267
1268 /*
1269 * If we're in an interrupt, have no user context or are running
1270 * in a region with pagefaults disabled then we must not take the fault
1271 */
1272 if (unlikely(faulthandler_disabled() || !mm)) {
1273 bad_area_nosemaphore(regs, error_code, address);
1274 return;
1275 }
1276
1277 /* Legacy check - remove this after verifying that it doesn't trigger */
1278 if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) {
1279 bad_area_nosemaphore(regs, error_code, address);
1280 return;
1281 }
1282
1283 local_irq_enable();
1284
1285 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1286
1287 /*
1288 * Read-only permissions can not be expressed in shadow stack PTEs.
1289 * Treat all shadow stack accesses as WRITE faults. This ensures
1290 * that the MM will prepare everything (e.g., break COW) such that
1291 * maybe_mkwrite() can create a proper shadow stack PTE.
1292 */
1293 if (error_code & X86_PF_SHSTK)
1294 flags |= FAULT_FLAG_WRITE;
1295 if (error_code & X86_PF_WRITE)
1296 flags |= FAULT_FLAG_WRITE;
1297 if (error_code & X86_PF_INSTR)
1298 flags |= FAULT_FLAG_INSTRUCTION;
1299
1300 /*
1301 * We set FAULT_FLAG_USER based on the register state, not
1302 * based on X86_PF_USER. User space accesses that cause
1303 * system page faults are still user accesses.
1304 */
1305 if (user_mode(regs))
1306 flags |= FAULT_FLAG_USER;
1307
1308#ifdef CONFIG_X86_64
1309 /*
1310 * Faults in the vsyscall page might need emulation. The
1311 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1312 * considered to be part of the user address space.
1313 *
1314 * The vsyscall page does not have a "real" VMA, so do this
1315 * emulation before we go searching for VMAs.
1316 *
1317 * PKRU never rejects instruction fetches, so we don't need
1318 * to consider the PF_PK bit.
1319 */
1320 if (is_vsyscall_vaddr(address)) {
1321 if (emulate_vsyscall(error_code, regs, address))
1322 return;
1323 }
1324#endif
1325
1326 if (!(flags & FAULT_FLAG_USER))
1327 goto lock_mmap;
1328
1329 vma = lock_vma_under_rcu(mm, address);
1330 if (!vma)
1331 goto lock_mmap;
1332
1333 if (unlikely(access_error(error_code, vma))) {
1334 bad_area_access_error(regs, error_code, address, NULL, vma);
1335 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
1336 return;
1337 }
1338 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
1339 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
1340 vma_end_read(vma);
1341
1342 if (!(fault & VM_FAULT_RETRY)) {
1343 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
1344 goto done;
1345 }
1346 count_vm_vma_lock_event(VMA_LOCK_RETRY);
1347 if (fault & VM_FAULT_MAJOR)
1348 flags |= FAULT_FLAG_TRIED;
1349
1350 /* Quick path to respond to signals */
1351 if (fault_signal_pending(fault, regs)) {
1352 if (!user_mode(regs))
1353 kernelmode_fixup_or_oops(regs, error_code, address,
1354 SIGBUS, BUS_ADRERR,
1355 ARCH_DEFAULT_PKEY);
1356 return;
1357 }
1358lock_mmap:
1359
1360retry:
1361 vma = lock_mm_and_find_vma(mm, address, regs);
1362 if (unlikely(!vma)) {
1363 bad_area_nosemaphore(regs, error_code, address);
1364 return;
1365 }
1366
1367 /*
1368 * Ok, we have a good vm_area for this memory access, so
1369 * we can handle it..
1370 */
1371 if (unlikely(access_error(error_code, vma))) {
1372 bad_area_access_error(regs, error_code, address, mm, vma);
1373 return;
1374 }
1375
1376 /*
1377 * If for any reason at all we couldn't handle the fault,
1378 * make sure we exit gracefully rather than endlessly redo
1379 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1380 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1381 *
1382 * Note that handle_userfault() may also release and reacquire mmap_lock
1383 * (and not return with VM_FAULT_RETRY), when returning to userland to
1384 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1385 * (potentially after handling any pending signal during the return to
1386 * userland). The return to userland is identified whenever
1387 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1388 */
1389 fault = handle_mm_fault(vma, address, flags, regs);
1390
1391 if (fault_signal_pending(fault, regs)) {
1392 /*
1393 * Quick path to respond to signals. The core mm code
1394 * has unlocked the mm for us if we get here.
1395 */
1396 if (!user_mode(regs))
1397 kernelmode_fixup_or_oops(regs, error_code, address,
1398 SIGBUS, BUS_ADRERR,
1399 ARCH_DEFAULT_PKEY);
1400 return;
1401 }
1402
1403 /* The fault is fully completed (including releasing mmap lock) */
1404 if (fault & VM_FAULT_COMPLETED)
1405 return;
1406
1407 /*
1408 * If we need to retry the mmap_lock has already been released,
1409 * and if there is a fatal signal pending there is no guarantee
1410 * that we made any progress. Handle this case first.
1411 */
1412 if (unlikely(fault & VM_FAULT_RETRY)) {
1413 flags |= FAULT_FLAG_TRIED;
1414 goto retry;
1415 }
1416
1417 mmap_read_unlock(mm);
1418done:
1419 if (likely(!(fault & VM_FAULT_ERROR)))
1420 return;
1421
1422 if (fatal_signal_pending(current) && !user_mode(regs)) {
1423 kernelmode_fixup_or_oops(regs, error_code, address,
1424 0, 0, ARCH_DEFAULT_PKEY);
1425 return;
1426 }
1427
1428 if (fault & VM_FAULT_OOM) {
1429 /* Kernel mode? Handle exceptions or die: */
1430 if (!user_mode(regs)) {
1431 kernelmode_fixup_or_oops(regs, error_code, address,
1432 SIGSEGV, SEGV_MAPERR,
1433 ARCH_DEFAULT_PKEY);
1434 return;
1435 }
1436
1437 /*
1438 * We ran out of memory, call the OOM killer, and return the
1439 * userspace (which will retry the fault, or kill us if we got
1440 * oom-killed):
1441 */
1442 pagefault_out_of_memory();
1443 } else {
1444 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1445 VM_FAULT_HWPOISON_LARGE))
1446 do_sigbus(regs, error_code, address, fault);
1447 else if (fault & VM_FAULT_SIGSEGV)
1448 bad_area_nosemaphore(regs, error_code, address);
1449 else
1450 BUG();
1451 }
1452}
1453NOKPROBE_SYMBOL(do_user_addr_fault);
1454
1455static __always_inline void
1456trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1457 unsigned long address)
1458{
1459 if (!trace_pagefault_enabled())
1460 return;
1461
1462 if (user_mode(regs))
1463 trace_page_fault_user(address, regs, error_code);
1464 else
1465 trace_page_fault_kernel(address, regs, error_code);
1466}
1467
1468static __always_inline void
1469handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1470 unsigned long address)
1471{
1472 trace_page_fault_entries(regs, error_code, address);
1473
1474 if (unlikely(kmmio_fault(regs, address)))
1475 return;
1476
1477 /* Was the fault on kernel-controlled part of the address space? */
1478 if (unlikely(fault_in_kernel_space(address))) {
1479 do_kern_addr_fault(regs, error_code, address);
1480 } else {
1481 do_user_addr_fault(regs, error_code, address);
1482 /*
1483 * User address page fault handling might have reenabled
1484 * interrupts. Fixing up all potential exit points of
1485 * do_user_addr_fault() and its leaf functions is just not
1486 * doable w/o creating an unholy mess or turning the code
1487 * upside down.
1488 */
1489 local_irq_disable();
1490 }
1491}
1492
1493DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1494{
1495 irqentry_state_t state;
1496 unsigned long address;
1497
1498 address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2();
1499
1500 prefetchw(¤t->mm->mmap_lock);
1501
1502 /*
1503 * KVM uses #PF vector to deliver 'page not present' events to guests
1504 * (asynchronous page fault mechanism). The event happens when a
1505 * userspace task is trying to access some valid (from guest's point of
1506 * view) memory which is not currently mapped by the host (e.g. the
1507 * memory is swapped out). Note, the corresponding "page ready" event
1508 * which is injected when the memory becomes available, is delivered via
1509 * an interrupt mechanism and not a #PF exception
1510 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1511 *
1512 * We are relying on the interrupted context being sane (valid RSP,
1513 * relevant locks not held, etc.), which is fine as long as the
1514 * interrupted context had IF=1. We are also relying on the KVM
1515 * async pf type field and CR2 being read consistently instead of
1516 * getting values from real and async page faults mixed up.
1517 *
1518 * Fingers crossed.
1519 *
1520 * The async #PF handling code takes care of idtentry handling
1521 * itself.
1522 */
1523 if (kvm_handle_async_pf(regs, (u32)address))
1524 return;
1525
1526 /*
1527 * Entry handling for valid #PF from kernel mode is slightly
1528 * different: RCU is already watching and ct_irq_enter() must not
1529 * be invoked because a kernel fault on a user space address might
1530 * sleep.
1531 *
1532 * In case the fault hit a RCU idle region the conditional entry
1533 * code reenabled RCU to avoid subsequent wreckage which helps
1534 * debuggability.
1535 */
1536 state = irqentry_enter(regs);
1537
1538 instrumentation_begin();
1539 handle_page_fault(regs, error_code, address);
1540 instrumentation_end();
1541
1542 irqentry_exit(regs, state);
1543}
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/kprobes.h> /* NOKPROBE_SYMBOL, ... */
13#include <linux/mmiotrace.h> /* kmmio_handler, ... */
14#include <linux/perf_event.h> /* perf_sw_event */
15#include <linux/hugetlb.h> /* hstate_index_to_shift */
16#include <linux/prefetch.h> /* prefetchw */
17#include <linux/context_tracking.h> /* exception_enter(), ... */
18#include <linux/uaccess.h> /* faulthandler_disabled() */
19#include <linux/efi.h> /* efi_recover_from_page_fault()*/
20#include <linux/mm_types.h>
21
22#include <asm/cpufeature.h> /* boot_cpu_has, ... */
23#include <asm/traps.h> /* dotraplinkage, ... */
24#include <asm/fixmap.h> /* VSYSCALL_ADDR */
25#include <asm/vsyscall.h> /* emulate_vsyscall */
26#include <asm/vm86.h> /* struct vm86 */
27#include <asm/mmu_context.h> /* vma_pkey() */
28#include <asm/efi.h> /* efi_recover_from_page_fault()*/
29#include <asm/desc.h> /* store_idt(), ... */
30#include <asm/cpu_entry_area.h> /* exception stack */
31#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
32#include <asm/kvm_para.h> /* kvm_handle_async_pf */
33
34#define CREATE_TRACE_POINTS
35#include <asm/trace/exceptions.h>
36
37/*
38 * Returns 0 if mmiotrace is disabled, or if the fault is not
39 * handled by mmiotrace:
40 */
41static nokprobe_inline int
42kmmio_fault(struct pt_regs *regs, unsigned long addr)
43{
44 if (unlikely(is_kmmio_active()))
45 if (kmmio_handler(regs, addr) == 1)
46 return -1;
47 return 0;
48}
49
50/*
51 * Prefetch quirks:
52 *
53 * 32-bit mode:
54 *
55 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
56 * Check that here and ignore it.
57 *
58 * 64-bit mode:
59 *
60 * Sometimes the CPU reports invalid exceptions on prefetch.
61 * Check that here and ignore it.
62 *
63 * Opcode checker based on code by Richard Brunner.
64 */
65static inline int
66check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
67 unsigned char opcode, int *prefetch)
68{
69 unsigned char instr_hi = opcode & 0xf0;
70 unsigned char instr_lo = opcode & 0x0f;
71
72 switch (instr_hi) {
73 case 0x20:
74 case 0x30:
75 /*
76 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
77 * In X86_64 long mode, the CPU will signal invalid
78 * opcode if some of these prefixes are present so
79 * X86_64 will never get here anyway
80 */
81 return ((instr_lo & 7) == 0x6);
82#ifdef CONFIG_X86_64
83 case 0x40:
84 /*
85 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
86 * Need to figure out under what instruction mode the
87 * instruction was issued. Could check the LDT for lm,
88 * but for now it's good enough to assume that long
89 * mode only uses well known segments or kernel.
90 */
91 return (!user_mode(regs) || user_64bit_mode(regs));
92#endif
93 case 0x60:
94 /* 0x64 thru 0x67 are valid prefixes in all modes. */
95 return (instr_lo & 0xC) == 0x4;
96 case 0xF0:
97 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
98 return !instr_lo || (instr_lo>>1) == 1;
99 case 0x00:
100 /* Prefetch instruction is 0x0F0D or 0x0F18 */
101 if (get_kernel_nofault(opcode, instr))
102 return 0;
103
104 *prefetch = (instr_lo == 0xF) &&
105 (opcode == 0x0D || opcode == 0x18);
106 return 0;
107 default:
108 return 0;
109 }
110}
111
112static int
113is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
114{
115 unsigned char *max_instr;
116 unsigned char *instr;
117 int prefetch = 0;
118
119 /*
120 * If it was a exec (instruction fetch) fault on NX page, then
121 * do not ignore the fault:
122 */
123 if (error_code & X86_PF_INSTR)
124 return 0;
125
126 instr = (void *)convert_ip_to_linear(current, regs);
127 max_instr = instr + 15;
128
129 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
130 return 0;
131
132 while (instr < max_instr) {
133 unsigned char opcode;
134
135 if (get_kernel_nofault(opcode, instr))
136 break;
137
138 instr++;
139
140 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
141 break;
142 }
143 return prefetch;
144}
145
146DEFINE_SPINLOCK(pgd_lock);
147LIST_HEAD(pgd_list);
148
149#ifdef CONFIG_X86_32
150static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
151{
152 unsigned index = pgd_index(address);
153 pgd_t *pgd_k;
154 p4d_t *p4d, *p4d_k;
155 pud_t *pud, *pud_k;
156 pmd_t *pmd, *pmd_k;
157
158 pgd += index;
159 pgd_k = init_mm.pgd + index;
160
161 if (!pgd_present(*pgd_k))
162 return NULL;
163
164 /*
165 * set_pgd(pgd, *pgd_k); here would be useless on PAE
166 * and redundant with the set_pmd() on non-PAE. As would
167 * set_p4d/set_pud.
168 */
169 p4d = p4d_offset(pgd, address);
170 p4d_k = p4d_offset(pgd_k, address);
171 if (!p4d_present(*p4d_k))
172 return NULL;
173
174 pud = pud_offset(p4d, address);
175 pud_k = pud_offset(p4d_k, address);
176 if (!pud_present(*pud_k))
177 return NULL;
178
179 pmd = pmd_offset(pud, address);
180 pmd_k = pmd_offset(pud_k, address);
181
182 if (pmd_present(*pmd) != pmd_present(*pmd_k))
183 set_pmd(pmd, *pmd_k);
184
185 if (!pmd_present(*pmd_k))
186 return NULL;
187 else
188 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
189
190 return pmd_k;
191}
192
193/*
194 * Handle a fault on the vmalloc or module mapping area
195 *
196 * This is needed because there is a race condition between the time
197 * when the vmalloc mapping code updates the PMD to the point in time
198 * where it synchronizes this update with the other page-tables in the
199 * system.
200 *
201 * In this race window another thread/CPU can map an area on the same
202 * PMD, finds it already present and does not synchronize it with the
203 * rest of the system yet. As a result v[mz]alloc might return areas
204 * which are not mapped in every page-table in the system, causing an
205 * unhandled page-fault when they are accessed.
206 */
207static noinline int vmalloc_fault(unsigned long address)
208{
209 unsigned long pgd_paddr;
210 pmd_t *pmd_k;
211 pte_t *pte_k;
212
213 /* Make sure we are in vmalloc area: */
214 if (!(address >= VMALLOC_START && address < VMALLOC_END))
215 return -1;
216
217 /*
218 * Synchronize this task's top level page-table
219 * with the 'reference' page table.
220 *
221 * Do _not_ use "current" here. We might be inside
222 * an interrupt in the middle of a task switch..
223 */
224 pgd_paddr = read_cr3_pa();
225 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
226 if (!pmd_k)
227 return -1;
228
229 if (pmd_large(*pmd_k))
230 return 0;
231
232 pte_k = pte_offset_kernel(pmd_k, address);
233 if (!pte_present(*pte_k))
234 return -1;
235
236 return 0;
237}
238NOKPROBE_SYMBOL(vmalloc_fault);
239
240void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
241{
242 unsigned long addr;
243
244 for (addr = start & PMD_MASK;
245 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
246 addr += PMD_SIZE) {
247 struct page *page;
248
249 spin_lock(&pgd_lock);
250 list_for_each_entry(page, &pgd_list, lru) {
251 spinlock_t *pgt_lock;
252
253 /* the pgt_lock only for Xen */
254 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
255
256 spin_lock(pgt_lock);
257 vmalloc_sync_one(page_address(page), addr);
258 spin_unlock(pgt_lock);
259 }
260 spin_unlock(&pgd_lock);
261 }
262}
263
264/*
265 * Did it hit the DOS screen memory VA from vm86 mode?
266 */
267static inline void
268check_v8086_mode(struct pt_regs *regs, unsigned long address,
269 struct task_struct *tsk)
270{
271#ifdef CONFIG_VM86
272 unsigned long bit;
273
274 if (!v8086_mode(regs) || !tsk->thread.vm86)
275 return;
276
277 bit = (address - 0xA0000) >> PAGE_SHIFT;
278 if (bit < 32)
279 tsk->thread.vm86->screen_bitmap |= 1 << bit;
280#endif
281}
282
283static bool low_pfn(unsigned long pfn)
284{
285 return pfn < max_low_pfn;
286}
287
288static void dump_pagetable(unsigned long address)
289{
290 pgd_t *base = __va(read_cr3_pa());
291 pgd_t *pgd = &base[pgd_index(address)];
292 p4d_t *p4d;
293 pud_t *pud;
294 pmd_t *pmd;
295 pte_t *pte;
296
297#ifdef CONFIG_X86_PAE
298 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
299 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
300 goto out;
301#define pr_pde pr_cont
302#else
303#define pr_pde pr_info
304#endif
305 p4d = p4d_offset(pgd, address);
306 pud = pud_offset(p4d, address);
307 pmd = pmd_offset(pud, address);
308 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
309#undef pr_pde
310
311 /*
312 * We must not directly access the pte in the highpte
313 * case if the page table is located in highmem.
314 * And let's rather not kmap-atomic the pte, just in case
315 * it's allocated already:
316 */
317 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
318 goto out;
319
320 pte = pte_offset_kernel(pmd, address);
321 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
322out:
323 pr_cont("\n");
324}
325
326#else /* CONFIG_X86_64: */
327
328#ifdef CONFIG_CPU_SUP_AMD
329static const char errata93_warning[] =
330KERN_ERR
331"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
332"******* Working around it, but it may cause SEGVs or burn power.\n"
333"******* Please consider a BIOS update.\n"
334"******* Disabling USB legacy in the BIOS may also help.\n";
335#endif
336
337/*
338 * No vm86 mode in 64-bit mode:
339 */
340static inline void
341check_v8086_mode(struct pt_regs *regs, unsigned long address,
342 struct task_struct *tsk)
343{
344}
345
346static int bad_address(void *p)
347{
348 unsigned long dummy;
349
350 return get_kernel_nofault(dummy, (unsigned long *)p);
351}
352
353static void dump_pagetable(unsigned long address)
354{
355 pgd_t *base = __va(read_cr3_pa());
356 pgd_t *pgd = base + pgd_index(address);
357 p4d_t *p4d;
358 pud_t *pud;
359 pmd_t *pmd;
360 pte_t *pte;
361
362 if (bad_address(pgd))
363 goto bad;
364
365 pr_info("PGD %lx ", pgd_val(*pgd));
366
367 if (!pgd_present(*pgd))
368 goto out;
369
370 p4d = p4d_offset(pgd, address);
371 if (bad_address(p4d))
372 goto bad;
373
374 pr_cont("P4D %lx ", p4d_val(*p4d));
375 if (!p4d_present(*p4d) || p4d_large(*p4d))
376 goto out;
377
378 pud = pud_offset(p4d, address);
379 if (bad_address(pud))
380 goto bad;
381
382 pr_cont("PUD %lx ", pud_val(*pud));
383 if (!pud_present(*pud) || pud_large(*pud))
384 goto out;
385
386 pmd = pmd_offset(pud, address);
387 if (bad_address(pmd))
388 goto bad;
389
390 pr_cont("PMD %lx ", pmd_val(*pmd));
391 if (!pmd_present(*pmd) || pmd_large(*pmd))
392 goto out;
393
394 pte = pte_offset_kernel(pmd, address);
395 if (bad_address(pte))
396 goto bad;
397
398 pr_cont("PTE %lx", pte_val(*pte));
399out:
400 pr_cont("\n");
401 return;
402bad:
403 pr_info("BAD\n");
404}
405
406#endif /* CONFIG_X86_64 */
407
408/*
409 * Workaround for K8 erratum #93 & buggy BIOS.
410 *
411 * BIOS SMM functions are required to use a specific workaround
412 * to avoid corruption of the 64bit RIP register on C stepping K8.
413 *
414 * A lot of BIOS that didn't get tested properly miss this.
415 *
416 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
417 * Try to work around it here.
418 *
419 * Note we only handle faults in kernel here.
420 * Does nothing on 32-bit.
421 */
422static int is_errata93(struct pt_regs *regs, unsigned long address)
423{
424#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
425 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
426 || boot_cpu_data.x86 != 0xf)
427 return 0;
428
429 if (address != regs->ip)
430 return 0;
431
432 if ((address >> 32) != 0)
433 return 0;
434
435 address |= 0xffffffffUL << 32;
436 if ((address >= (u64)_stext && address <= (u64)_etext) ||
437 (address >= MODULES_VADDR && address <= MODULES_END)) {
438 printk_once(errata93_warning);
439 regs->ip = address;
440 return 1;
441 }
442#endif
443 return 0;
444}
445
446/*
447 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
448 * to illegal addresses >4GB.
449 *
450 * We catch this in the page fault handler because these addresses
451 * are not reachable. Just detect this case and return. Any code
452 * segment in LDT is compatibility mode.
453 */
454static int is_errata100(struct pt_regs *regs, unsigned long address)
455{
456#ifdef CONFIG_X86_64
457 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
458 return 1;
459#endif
460 return 0;
461}
462
463/* Pentium F0 0F C7 C8 bug workaround: */
464static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
465{
466#ifdef CONFIG_X86_F00F_BUG
467 if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) {
468 handle_invalid_op(regs);
469 return 1;
470 }
471#endif
472 return 0;
473}
474
475static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
476{
477 u32 offset = (index >> 3) * sizeof(struct desc_struct);
478 unsigned long addr;
479 struct ldttss_desc desc;
480
481 if (index == 0) {
482 pr_alert("%s: NULL\n", name);
483 return;
484 }
485
486 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
487 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
488 return;
489 }
490
491 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
492 sizeof(struct ldttss_desc))) {
493 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
494 name, index);
495 return;
496 }
497
498 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
499#ifdef CONFIG_X86_64
500 addr |= ((u64)desc.base3 << 32);
501#endif
502 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
503 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
504}
505
506static void
507show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
508{
509 if (!oops_may_print())
510 return;
511
512 if (error_code & X86_PF_INSTR) {
513 unsigned int level;
514 pgd_t *pgd;
515 pte_t *pte;
516
517 pgd = __va(read_cr3_pa());
518 pgd += pgd_index(address);
519
520 pte = lookup_address_in_pgd(pgd, address, &level);
521
522 if (pte && pte_present(*pte) && !pte_exec(*pte))
523 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
524 from_kuid(&init_user_ns, current_uid()));
525 if (pte && pte_present(*pte) && pte_exec(*pte) &&
526 (pgd_flags(*pgd) & _PAGE_USER) &&
527 (__read_cr4() & X86_CR4_SMEP))
528 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
529 from_kuid(&init_user_ns, current_uid()));
530 }
531
532 if (address < PAGE_SIZE && !user_mode(regs))
533 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
534 (void *)address);
535 else
536 pr_alert("BUG: unable to handle page fault for address: %px\n",
537 (void *)address);
538
539 pr_alert("#PF: %s %s in %s mode\n",
540 (error_code & X86_PF_USER) ? "user" : "supervisor",
541 (error_code & X86_PF_INSTR) ? "instruction fetch" :
542 (error_code & X86_PF_WRITE) ? "write access" :
543 "read access",
544 user_mode(regs) ? "user" : "kernel");
545 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
546 !(error_code & X86_PF_PROT) ? "not-present page" :
547 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
548 (error_code & X86_PF_PK) ? "protection keys violation" :
549 "permissions violation");
550
551 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
552 struct desc_ptr idt, gdt;
553 u16 ldtr, tr;
554
555 /*
556 * This can happen for quite a few reasons. The more obvious
557 * ones are faults accessing the GDT, or LDT. Perhaps
558 * surprisingly, if the CPU tries to deliver a benign or
559 * contributory exception from user code and gets a page fault
560 * during delivery, the page fault can be delivered as though
561 * it originated directly from user code. This could happen
562 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
563 * kernel or IST stack.
564 */
565 store_idt(&idt);
566
567 /* Usable even on Xen PV -- it's just slow. */
568 native_store_gdt(&gdt);
569
570 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
571 idt.address, idt.size, gdt.address, gdt.size);
572
573 store_ldt(ldtr);
574 show_ldttss(&gdt, "LDTR", ldtr);
575
576 store_tr(tr);
577 show_ldttss(&gdt, "TR", tr);
578 }
579
580 dump_pagetable(address);
581}
582
583static noinline void
584pgtable_bad(struct pt_regs *regs, unsigned long error_code,
585 unsigned long address)
586{
587 struct task_struct *tsk;
588 unsigned long flags;
589 int sig;
590
591 flags = oops_begin();
592 tsk = current;
593 sig = SIGKILL;
594
595 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
596 tsk->comm, address);
597 dump_pagetable(address);
598
599 if (__die("Bad pagetable", regs, error_code))
600 sig = 0;
601
602 oops_end(flags, regs, sig);
603}
604
605static void set_signal_archinfo(unsigned long address,
606 unsigned long error_code)
607{
608 struct task_struct *tsk = current;
609
610 /*
611 * To avoid leaking information about the kernel page
612 * table layout, pretend that user-mode accesses to
613 * kernel addresses are always protection faults.
614 *
615 * NB: This means that failed vsyscalls with vsyscall=none
616 * will have the PROT bit. This doesn't leak any
617 * information and does not appear to cause any problems.
618 */
619 if (address >= TASK_SIZE_MAX)
620 error_code |= X86_PF_PROT;
621
622 tsk->thread.trap_nr = X86_TRAP_PF;
623 tsk->thread.error_code = error_code | X86_PF_USER;
624 tsk->thread.cr2 = address;
625}
626
627static noinline void
628no_context(struct pt_regs *regs, unsigned long error_code,
629 unsigned long address, int signal, int si_code)
630{
631 struct task_struct *tsk = current;
632 unsigned long flags;
633 int sig;
634
635 if (user_mode(regs)) {
636 /*
637 * This is an implicit supervisor-mode access from user
638 * mode. Bypass all the kernel-mode recovery code and just
639 * OOPS.
640 */
641 goto oops;
642 }
643
644 /* Are we prepared to handle this kernel fault? */
645 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
646 /*
647 * Any interrupt that takes a fault gets the fixup. This makes
648 * the below recursive fault logic only apply to a faults from
649 * task context.
650 */
651 if (in_interrupt())
652 return;
653
654 /*
655 * Per the above we're !in_interrupt(), aka. task context.
656 *
657 * In this case we need to make sure we're not recursively
658 * faulting through the emulate_vsyscall() logic.
659 */
660 if (current->thread.sig_on_uaccess_err && signal) {
661 set_signal_archinfo(address, error_code);
662
663 /* XXX: hwpoison faults will set the wrong code. */
664 force_sig_fault(signal, si_code, (void __user *)address);
665 }
666
667 /*
668 * Barring that, we can do the fixup and be happy.
669 */
670 return;
671 }
672
673#ifdef CONFIG_VMAP_STACK
674 /*
675 * Stack overflow? During boot, we can fault near the initial
676 * stack in the direct map, but that's not an overflow -- check
677 * that we're in vmalloc space to avoid this.
678 */
679 if (is_vmalloc_addr((void *)address) &&
680 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
681 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
682 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
683 /*
684 * We're likely to be running with very little stack space
685 * left. It's plausible that we'd hit this condition but
686 * double-fault even before we get this far, in which case
687 * we're fine: the double-fault handler will deal with it.
688 *
689 * We don't want to make it all the way into the oops code
690 * and then double-fault, though, because we're likely to
691 * break the console driver and lose most of the stack dump.
692 */
693 asm volatile ("movq %[stack], %%rsp\n\t"
694 "call handle_stack_overflow\n\t"
695 "1: jmp 1b"
696 : ASM_CALL_CONSTRAINT
697 : "D" ("kernel stack overflow (page fault)"),
698 "S" (regs), "d" (address),
699 [stack] "rm" (stack));
700 unreachable();
701 }
702#endif
703
704 /*
705 * 32-bit:
706 *
707 * Valid to do another page fault here, because if this fault
708 * had been triggered by is_prefetch fixup_exception would have
709 * handled it.
710 *
711 * 64-bit:
712 *
713 * Hall of shame of CPU/BIOS bugs.
714 */
715 if (is_prefetch(regs, error_code, address))
716 return;
717
718 if (is_errata93(regs, address))
719 return;
720
721 /*
722 * Buggy firmware could access regions which might page fault, try to
723 * recover from such faults.
724 */
725 if (IS_ENABLED(CONFIG_EFI))
726 efi_recover_from_page_fault(address);
727
728oops:
729 /*
730 * Oops. The kernel tried to access some bad page. We'll have to
731 * terminate things with extreme prejudice:
732 */
733 flags = oops_begin();
734
735 show_fault_oops(regs, error_code, address);
736
737 if (task_stack_end_corrupted(tsk))
738 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
739
740 sig = SIGKILL;
741 if (__die("Oops", regs, error_code))
742 sig = 0;
743
744 /* Executive summary in case the body of the oops scrolled away */
745 printk(KERN_DEFAULT "CR2: %016lx\n", address);
746
747 oops_end(flags, regs, sig);
748}
749
750/*
751 * Print out info about fatal segfaults, if the show_unhandled_signals
752 * sysctl is set:
753 */
754static inline void
755show_signal_msg(struct pt_regs *regs, unsigned long error_code,
756 unsigned long address, struct task_struct *tsk)
757{
758 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
759
760 if (!unhandled_signal(tsk, SIGSEGV))
761 return;
762
763 if (!printk_ratelimit())
764 return;
765
766 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
767 loglvl, tsk->comm, task_pid_nr(tsk), address,
768 (void *)regs->ip, (void *)regs->sp, error_code);
769
770 print_vma_addr(KERN_CONT " in ", regs->ip);
771
772 printk(KERN_CONT "\n");
773
774 show_opcodes(regs, loglvl);
775}
776
777/*
778 * The (legacy) vsyscall page is the long page in the kernel portion
779 * of the address space that has user-accessible permissions.
780 */
781static bool is_vsyscall_vaddr(unsigned long vaddr)
782{
783 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
784}
785
786static void
787__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
788 unsigned long address, u32 pkey, int si_code)
789{
790 struct task_struct *tsk = current;
791
792 /* User mode accesses just cause a SIGSEGV */
793 if (user_mode(regs) && (error_code & X86_PF_USER)) {
794 /*
795 * It's possible to have interrupts off here:
796 */
797 local_irq_enable();
798
799 /*
800 * Valid to do another page fault here because this one came
801 * from user space:
802 */
803 if (is_prefetch(regs, error_code, address))
804 return;
805
806 if (is_errata100(regs, address))
807 return;
808
809 /*
810 * To avoid leaking information about the kernel page table
811 * layout, pretend that user-mode accesses to kernel addresses
812 * are always protection faults.
813 */
814 if (address >= TASK_SIZE_MAX)
815 error_code |= X86_PF_PROT;
816
817 if (likely(show_unhandled_signals))
818 show_signal_msg(regs, error_code, address, tsk);
819
820 set_signal_archinfo(address, error_code);
821
822 if (si_code == SEGV_PKUERR)
823 force_sig_pkuerr((void __user *)address, pkey);
824
825 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
826
827 local_irq_disable();
828
829 return;
830 }
831
832 if (is_f00f_bug(regs, address))
833 return;
834
835 no_context(regs, error_code, address, SIGSEGV, si_code);
836}
837
838static noinline void
839bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
840 unsigned long address)
841{
842 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
843}
844
845static void
846__bad_area(struct pt_regs *regs, unsigned long error_code,
847 unsigned long address, u32 pkey, int si_code)
848{
849 struct mm_struct *mm = current->mm;
850 /*
851 * Something tried to access memory that isn't in our memory map..
852 * Fix it, but check if it's kernel or user first..
853 */
854 mmap_read_unlock(mm);
855
856 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
857}
858
859static noinline void
860bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
861{
862 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
863}
864
865static inline bool bad_area_access_from_pkeys(unsigned long error_code,
866 struct vm_area_struct *vma)
867{
868 /* This code is always called on the current mm */
869 bool foreign = false;
870
871 if (!boot_cpu_has(X86_FEATURE_OSPKE))
872 return false;
873 if (error_code & X86_PF_PK)
874 return true;
875 /* this checks permission keys on the VMA: */
876 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
877 (error_code & X86_PF_INSTR), foreign))
878 return true;
879 return false;
880}
881
882static noinline void
883bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
884 unsigned long address, struct vm_area_struct *vma)
885{
886 /*
887 * This OSPKE check is not strictly necessary at runtime.
888 * But, doing it this way allows compiler optimizations
889 * if pkeys are compiled out.
890 */
891 if (bad_area_access_from_pkeys(error_code, vma)) {
892 /*
893 * A protection key fault means that the PKRU value did not allow
894 * access to some PTE. Userspace can figure out what PKRU was
895 * from the XSAVE state. This function captures the pkey from
896 * the vma and passes it to userspace so userspace can discover
897 * which protection key was set on the PTE.
898 *
899 * If we get here, we know that the hardware signaled a X86_PF_PK
900 * fault and that there was a VMA once we got in the fault
901 * handler. It does *not* guarantee that the VMA we find here
902 * was the one that we faulted on.
903 *
904 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
905 * 2. T1 : set PKRU to deny access to pkey=4, touches page
906 * 3. T1 : faults...
907 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
908 * 5. T1 : enters fault handler, takes mmap_lock, etc...
909 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
910 * faulted on a pte with its pkey=4.
911 */
912 u32 pkey = vma_pkey(vma);
913
914 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
915 } else {
916 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
917 }
918}
919
920static void
921do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
922 vm_fault_t fault)
923{
924 /* Kernel mode? Handle exceptions or die: */
925 if (!(error_code & X86_PF_USER)) {
926 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
927 return;
928 }
929
930 /* User-space => ok to do another page fault: */
931 if (is_prefetch(regs, error_code, address))
932 return;
933
934 set_signal_archinfo(address, error_code);
935
936#ifdef CONFIG_MEMORY_FAILURE
937 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
938 struct task_struct *tsk = current;
939 unsigned lsb = 0;
940
941 pr_err(
942 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
943 tsk->comm, tsk->pid, address);
944 if (fault & VM_FAULT_HWPOISON_LARGE)
945 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
946 if (fault & VM_FAULT_HWPOISON)
947 lsb = PAGE_SHIFT;
948 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
949 return;
950 }
951#endif
952 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
953}
954
955static noinline void
956mm_fault_error(struct pt_regs *regs, unsigned long error_code,
957 unsigned long address, vm_fault_t fault)
958{
959 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
960 no_context(regs, error_code, address, 0, 0);
961 return;
962 }
963
964 if (fault & VM_FAULT_OOM) {
965 /* Kernel mode? Handle exceptions or die: */
966 if (!(error_code & X86_PF_USER)) {
967 no_context(regs, error_code, address,
968 SIGSEGV, SEGV_MAPERR);
969 return;
970 }
971
972 /*
973 * We ran out of memory, call the OOM killer, and return the
974 * userspace (which will retry the fault, or kill us if we got
975 * oom-killed):
976 */
977 pagefault_out_of_memory();
978 } else {
979 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
980 VM_FAULT_HWPOISON_LARGE))
981 do_sigbus(regs, error_code, address, fault);
982 else if (fault & VM_FAULT_SIGSEGV)
983 bad_area_nosemaphore(regs, error_code, address);
984 else
985 BUG();
986 }
987}
988
989static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
990{
991 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
992 return 0;
993
994 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
995 return 0;
996
997 return 1;
998}
999
1000/*
1001 * Handle a spurious fault caused by a stale TLB entry.
1002 *
1003 * This allows us to lazily refresh the TLB when increasing the
1004 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1005 * eagerly is very expensive since that implies doing a full
1006 * cross-processor TLB flush, even if no stale TLB entries exist
1007 * on other processors.
1008 *
1009 * Spurious faults may only occur if the TLB contains an entry with
1010 * fewer permission than the page table entry. Non-present (P = 0)
1011 * and reserved bit (R = 1) faults are never spurious.
1012 *
1013 * There are no security implications to leaving a stale TLB when
1014 * increasing the permissions on a page.
1015 *
1016 * Returns non-zero if a spurious fault was handled, zero otherwise.
1017 *
1018 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1019 * (Optional Invalidation).
1020 */
1021static noinline int
1022spurious_kernel_fault(unsigned long error_code, unsigned long address)
1023{
1024 pgd_t *pgd;
1025 p4d_t *p4d;
1026 pud_t *pud;
1027 pmd_t *pmd;
1028 pte_t *pte;
1029 int ret;
1030
1031 /*
1032 * Only writes to RO or instruction fetches from NX may cause
1033 * spurious faults.
1034 *
1035 * These could be from user or supervisor accesses but the TLB
1036 * is only lazily flushed after a kernel mapping protection
1037 * change, so user accesses are not expected to cause spurious
1038 * faults.
1039 */
1040 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1041 error_code != (X86_PF_INSTR | X86_PF_PROT))
1042 return 0;
1043
1044 pgd = init_mm.pgd + pgd_index(address);
1045 if (!pgd_present(*pgd))
1046 return 0;
1047
1048 p4d = p4d_offset(pgd, address);
1049 if (!p4d_present(*p4d))
1050 return 0;
1051
1052 if (p4d_large(*p4d))
1053 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1054
1055 pud = pud_offset(p4d, address);
1056 if (!pud_present(*pud))
1057 return 0;
1058
1059 if (pud_large(*pud))
1060 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1061
1062 pmd = pmd_offset(pud, address);
1063 if (!pmd_present(*pmd))
1064 return 0;
1065
1066 if (pmd_large(*pmd))
1067 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1068
1069 pte = pte_offset_kernel(pmd, address);
1070 if (!pte_present(*pte))
1071 return 0;
1072
1073 ret = spurious_kernel_fault_check(error_code, pte);
1074 if (!ret)
1075 return 0;
1076
1077 /*
1078 * Make sure we have permissions in PMD.
1079 * If not, then there's a bug in the page tables:
1080 */
1081 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1082 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1083
1084 return ret;
1085}
1086NOKPROBE_SYMBOL(spurious_kernel_fault);
1087
1088int show_unhandled_signals = 1;
1089
1090static inline int
1091access_error(unsigned long error_code, struct vm_area_struct *vma)
1092{
1093 /* This is only called for the current mm, so: */
1094 bool foreign = false;
1095
1096 /*
1097 * Read or write was blocked by protection keys. This is
1098 * always an unconditional error and can never result in
1099 * a follow-up action to resolve the fault, like a COW.
1100 */
1101 if (error_code & X86_PF_PK)
1102 return 1;
1103
1104 /*
1105 * Make sure to check the VMA so that we do not perform
1106 * faults just to hit a X86_PF_PK as soon as we fill in a
1107 * page.
1108 */
1109 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1110 (error_code & X86_PF_INSTR), foreign))
1111 return 1;
1112
1113 if (error_code & X86_PF_WRITE) {
1114 /* write, present and write, not present: */
1115 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1116 return 1;
1117 return 0;
1118 }
1119
1120 /* read, present: */
1121 if (unlikely(error_code & X86_PF_PROT))
1122 return 1;
1123
1124 /* read, not present: */
1125 if (unlikely(!vma_is_accessible(vma)))
1126 return 1;
1127
1128 return 0;
1129}
1130
1131static int fault_in_kernel_space(unsigned long address)
1132{
1133 /*
1134 * On 64-bit systems, the vsyscall page is at an address above
1135 * TASK_SIZE_MAX, but is not considered part of the kernel
1136 * address space.
1137 */
1138 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1139 return false;
1140
1141 return address >= TASK_SIZE_MAX;
1142}
1143
1144/*
1145 * Called for all faults where 'address' is part of the kernel address
1146 * space. Might get called for faults that originate from *code* that
1147 * ran in userspace or the kernel.
1148 */
1149static void
1150do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1151 unsigned long address)
1152{
1153 /*
1154 * Protection keys exceptions only happen on user pages. We
1155 * have no user pages in the kernel portion of the address
1156 * space, so do not expect them here.
1157 */
1158 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1159
1160#ifdef CONFIG_X86_32
1161 /*
1162 * We can fault-in kernel-space virtual memory on-demand. The
1163 * 'reference' page table is init_mm.pgd.
1164 *
1165 * NOTE! We MUST NOT take any locks for this case. We may
1166 * be in an interrupt or a critical region, and should
1167 * only copy the information from the master page table,
1168 * nothing more.
1169 *
1170 * Before doing this on-demand faulting, ensure that the
1171 * fault is not any of the following:
1172 * 1. A fault on a PTE with a reserved bit set.
1173 * 2. A fault caused by a user-mode access. (Do not demand-
1174 * fault kernel memory due to user-mode accesses).
1175 * 3. A fault caused by a page-level protection violation.
1176 * (A demand fault would be on a non-present page which
1177 * would have X86_PF_PROT==0).
1178 *
1179 * This is only needed to close a race condition on x86-32 in
1180 * the vmalloc mapping/unmapping code. See the comment above
1181 * vmalloc_fault() for details. On x86-64 the race does not
1182 * exist as the vmalloc mappings don't need to be synchronized
1183 * there.
1184 */
1185 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1186 if (vmalloc_fault(address) >= 0)
1187 return;
1188 }
1189#endif
1190
1191 /* Was the fault spurious, caused by lazy TLB invalidation? */
1192 if (spurious_kernel_fault(hw_error_code, address))
1193 return;
1194
1195 /* kprobes don't want to hook the spurious faults: */
1196 if (kprobe_page_fault(regs, X86_TRAP_PF))
1197 return;
1198
1199 /*
1200 * Note, despite being a "bad area", there are quite a few
1201 * acceptable reasons to get here, such as erratum fixups
1202 * and handling kernel code that can fault, like get_user().
1203 *
1204 * Don't take the mm semaphore here. If we fixup a prefetch
1205 * fault we could otherwise deadlock:
1206 */
1207 bad_area_nosemaphore(regs, hw_error_code, address);
1208}
1209NOKPROBE_SYMBOL(do_kern_addr_fault);
1210
1211/* Handle faults in the user portion of the address space */
1212static inline
1213void do_user_addr_fault(struct pt_regs *regs,
1214 unsigned long hw_error_code,
1215 unsigned long address)
1216{
1217 struct vm_area_struct *vma;
1218 struct task_struct *tsk;
1219 struct mm_struct *mm;
1220 vm_fault_t fault;
1221 unsigned int flags = FAULT_FLAG_DEFAULT;
1222
1223 tsk = current;
1224 mm = tsk->mm;
1225
1226 /* kprobes don't want to hook the spurious faults: */
1227 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
1228 return;
1229
1230 /*
1231 * Reserved bits are never expected to be set on
1232 * entries in the user portion of the page tables.
1233 */
1234 if (unlikely(hw_error_code & X86_PF_RSVD))
1235 pgtable_bad(regs, hw_error_code, address);
1236
1237 /*
1238 * If SMAP is on, check for invalid kernel (supervisor) access to user
1239 * pages in the user address space. The odd case here is WRUSS,
1240 * which, according to the preliminary documentation, does not respect
1241 * SMAP and will have the USER bit set so, in all cases, SMAP
1242 * enforcement appears to be consistent with the USER bit.
1243 */
1244 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1245 !(hw_error_code & X86_PF_USER) &&
1246 !(regs->flags & X86_EFLAGS_AC)))
1247 {
1248 bad_area_nosemaphore(regs, hw_error_code, address);
1249 return;
1250 }
1251
1252 /*
1253 * If we're in an interrupt, have no user context or are running
1254 * in a region with pagefaults disabled then we must not take the fault
1255 */
1256 if (unlikely(faulthandler_disabled() || !mm)) {
1257 bad_area_nosemaphore(regs, hw_error_code, address);
1258 return;
1259 }
1260
1261 /*
1262 * It's safe to allow irq's after cr2 has been saved and the
1263 * vmalloc fault has been handled.
1264 *
1265 * User-mode registers count as a user access even for any
1266 * potential system fault or CPU buglet:
1267 */
1268 if (user_mode(regs)) {
1269 local_irq_enable();
1270 flags |= FAULT_FLAG_USER;
1271 } else {
1272 if (regs->flags & X86_EFLAGS_IF)
1273 local_irq_enable();
1274 }
1275
1276 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1277
1278 if (hw_error_code & X86_PF_WRITE)
1279 flags |= FAULT_FLAG_WRITE;
1280 if (hw_error_code & X86_PF_INSTR)
1281 flags |= FAULT_FLAG_INSTRUCTION;
1282
1283#ifdef CONFIG_X86_64
1284 /*
1285 * Faults in the vsyscall page might need emulation. The
1286 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1287 * considered to be part of the user address space.
1288 *
1289 * The vsyscall page does not have a "real" VMA, so do this
1290 * emulation before we go searching for VMAs.
1291 *
1292 * PKRU never rejects instruction fetches, so we don't need
1293 * to consider the PF_PK bit.
1294 */
1295 if (is_vsyscall_vaddr(address)) {
1296 if (emulate_vsyscall(hw_error_code, regs, address))
1297 return;
1298 }
1299#endif
1300
1301 /*
1302 * Kernel-mode access to the user address space should only occur
1303 * on well-defined single instructions listed in the exception
1304 * tables. But, an erroneous kernel fault occurring outside one of
1305 * those areas which also holds mmap_lock might deadlock attempting
1306 * to validate the fault against the address space.
1307 *
1308 * Only do the expensive exception table search when we might be at
1309 * risk of a deadlock. This happens if we
1310 * 1. Failed to acquire mmap_lock, and
1311 * 2. The access did not originate in userspace.
1312 */
1313 if (unlikely(!mmap_read_trylock(mm))) {
1314 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1315 /*
1316 * Fault from code in kernel from
1317 * which we do not expect faults.
1318 */
1319 bad_area_nosemaphore(regs, hw_error_code, address);
1320 return;
1321 }
1322retry:
1323 mmap_read_lock(mm);
1324 } else {
1325 /*
1326 * The above down_read_trylock() might have succeeded in
1327 * which case we'll have missed the might_sleep() from
1328 * down_read():
1329 */
1330 might_sleep();
1331 }
1332
1333 vma = find_vma(mm, address);
1334 if (unlikely(!vma)) {
1335 bad_area(regs, hw_error_code, address);
1336 return;
1337 }
1338 if (likely(vma->vm_start <= address))
1339 goto good_area;
1340 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1341 bad_area(regs, hw_error_code, address);
1342 return;
1343 }
1344 if (unlikely(expand_stack(vma, address))) {
1345 bad_area(regs, hw_error_code, address);
1346 return;
1347 }
1348
1349 /*
1350 * Ok, we have a good vm_area for this memory access, so
1351 * we can handle it..
1352 */
1353good_area:
1354 if (unlikely(access_error(hw_error_code, vma))) {
1355 bad_area_access_error(regs, hw_error_code, address, vma);
1356 return;
1357 }
1358
1359 /*
1360 * If for any reason at all we couldn't handle the fault,
1361 * make sure we exit gracefully rather than endlessly redo
1362 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1363 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1364 *
1365 * Note that handle_userfault() may also release and reacquire mmap_lock
1366 * (and not return with VM_FAULT_RETRY), when returning to userland to
1367 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1368 * (potentially after handling any pending signal during the return to
1369 * userland). The return to userland is identified whenever
1370 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1371 */
1372 fault = handle_mm_fault(vma, address, flags, regs);
1373
1374 /* Quick path to respond to signals */
1375 if (fault_signal_pending(fault, regs)) {
1376 if (!user_mode(regs))
1377 no_context(regs, hw_error_code, address, SIGBUS,
1378 BUS_ADRERR);
1379 return;
1380 }
1381
1382 /*
1383 * If we need to retry the mmap_lock has already been released,
1384 * and if there is a fatal signal pending there is no guarantee
1385 * that we made any progress. Handle this case first.
1386 */
1387 if (unlikely((fault & VM_FAULT_RETRY) &&
1388 (flags & FAULT_FLAG_ALLOW_RETRY))) {
1389 flags |= FAULT_FLAG_TRIED;
1390 goto retry;
1391 }
1392
1393 mmap_read_unlock(mm);
1394 if (unlikely(fault & VM_FAULT_ERROR)) {
1395 mm_fault_error(regs, hw_error_code, address, fault);
1396 return;
1397 }
1398
1399 check_v8086_mode(regs, address, tsk);
1400}
1401NOKPROBE_SYMBOL(do_user_addr_fault);
1402
1403static __always_inline void
1404trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1405 unsigned long address)
1406{
1407 if (!trace_pagefault_enabled())
1408 return;
1409
1410 if (user_mode(regs))
1411 trace_page_fault_user(address, regs, error_code);
1412 else
1413 trace_page_fault_kernel(address, regs, error_code);
1414}
1415
1416static __always_inline void
1417handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1418 unsigned long address)
1419{
1420 trace_page_fault_entries(regs, error_code, address);
1421
1422 if (unlikely(kmmio_fault(regs, address)))
1423 return;
1424
1425 /* Was the fault on kernel-controlled part of the address space? */
1426 if (unlikely(fault_in_kernel_space(address))) {
1427 do_kern_addr_fault(regs, error_code, address);
1428 } else {
1429 do_user_addr_fault(regs, error_code, address);
1430 /*
1431 * User address page fault handling might have reenabled
1432 * interrupts. Fixing up all potential exit points of
1433 * do_user_addr_fault() and its leaf functions is just not
1434 * doable w/o creating an unholy mess or turning the code
1435 * upside down.
1436 */
1437 local_irq_disable();
1438 }
1439}
1440
1441DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1442{
1443 unsigned long address = read_cr2();
1444 irqentry_state_t state;
1445
1446 prefetchw(¤t->mm->mmap_lock);
1447
1448 /*
1449 * KVM has two types of events that are, logically, interrupts, but
1450 * are unfortunately delivered using the #PF vector. These events are
1451 * "you just accessed valid memory, but the host doesn't have it right
1452 * now, so I'll put you to sleep if you continue" and "that memory
1453 * you tried to access earlier is available now."
1454 *
1455 * We are relying on the interrupted context being sane (valid RSP,
1456 * relevant locks not held, etc.), which is fine as long as the
1457 * interrupted context had IF=1. We are also relying on the KVM
1458 * async pf type field and CR2 being read consistently instead of
1459 * getting values from real and async page faults mixed up.
1460 *
1461 * Fingers crossed.
1462 *
1463 * The async #PF handling code takes care of idtentry handling
1464 * itself.
1465 */
1466 if (kvm_handle_async_pf(regs, (u32)address))
1467 return;
1468
1469 /*
1470 * Entry handling for valid #PF from kernel mode is slightly
1471 * different: RCU is already watching and rcu_irq_enter() must not
1472 * be invoked because a kernel fault on a user space address might
1473 * sleep.
1474 *
1475 * In case the fault hit a RCU idle region the conditional entry
1476 * code reenabled RCU to avoid subsequent wreckage which helps
1477 * debugability.
1478 */
1479 state = irqentry_enter(regs);
1480
1481 instrumentation_begin();
1482 handle_page_fault(regs, error_code, address);
1483 instrumentation_end();
1484
1485 irqentry_exit(regs, state);
1486}