Loading...
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/bootmem.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
20#include <asm/cpufeature.h> /* boot_cpu_has, ... */
21#include <asm/traps.h> /* dotraplinkage, ... */
22#include <asm/pgalloc.h> /* pgd_*(), ... */
23#include <asm/fixmap.h> /* VSYSCALL_ADDR */
24#include <asm/vsyscall.h> /* emulate_vsyscall */
25#include <asm/vm86.h> /* struct vm86 */
26#include <asm/mmu_context.h> /* vma_pkey() */
27
28#define CREATE_TRACE_POINTS
29#include <asm/trace/exceptions.h>
30
31/*
32 * Returns 0 if mmiotrace is disabled, or if the fault is not
33 * handled by mmiotrace:
34 */
35static nokprobe_inline int
36kmmio_fault(struct pt_regs *regs, unsigned long addr)
37{
38 if (unlikely(is_kmmio_active()))
39 if (kmmio_handler(regs, addr) == 1)
40 return -1;
41 return 0;
42}
43
44static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
45{
46 int ret = 0;
47
48 /* kprobe_running() needs smp_processor_id() */
49 if (kprobes_built_in() && !user_mode(regs)) {
50 preempt_disable();
51 if (kprobe_running() && kprobe_fault_handler(regs, 14))
52 ret = 1;
53 preempt_enable();
54 }
55
56 return ret;
57}
58
59/*
60 * Prefetch quirks:
61 *
62 * 32-bit mode:
63 *
64 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
65 * Check that here and ignore it.
66 *
67 * 64-bit mode:
68 *
69 * Sometimes the CPU reports invalid exceptions on prefetch.
70 * Check that here and ignore it.
71 *
72 * Opcode checker based on code by Richard Brunner.
73 */
74static inline int
75check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
76 unsigned char opcode, int *prefetch)
77{
78 unsigned char instr_hi = opcode & 0xf0;
79 unsigned char instr_lo = opcode & 0x0f;
80
81 switch (instr_hi) {
82 case 0x20:
83 case 0x30:
84 /*
85 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
86 * In X86_64 long mode, the CPU will signal invalid
87 * opcode if some of these prefixes are present so
88 * X86_64 will never get here anyway
89 */
90 return ((instr_lo & 7) == 0x6);
91#ifdef CONFIG_X86_64
92 case 0x40:
93 /*
94 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
95 * Need to figure out under what instruction mode the
96 * instruction was issued. Could check the LDT for lm,
97 * but for now it's good enough to assume that long
98 * mode only uses well known segments or kernel.
99 */
100 return (!user_mode(regs) || user_64bit_mode(regs));
101#endif
102 case 0x60:
103 /* 0x64 thru 0x67 are valid prefixes in all modes. */
104 return (instr_lo & 0xC) == 0x4;
105 case 0xF0:
106 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
107 return !instr_lo || (instr_lo>>1) == 1;
108 case 0x00:
109 /* Prefetch instruction is 0x0F0D or 0x0F18 */
110 if (probe_kernel_address(instr, opcode))
111 return 0;
112
113 *prefetch = (instr_lo == 0xF) &&
114 (opcode == 0x0D || opcode == 0x18);
115 return 0;
116 default:
117 return 0;
118 }
119}
120
121static int
122is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
123{
124 unsigned char *max_instr;
125 unsigned char *instr;
126 int prefetch = 0;
127
128 /*
129 * If it was a exec (instruction fetch) fault on NX page, then
130 * do not ignore the fault:
131 */
132 if (error_code & X86_PF_INSTR)
133 return 0;
134
135 instr = (void *)convert_ip_to_linear(current, regs);
136 max_instr = instr + 15;
137
138 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
139 return 0;
140
141 while (instr < max_instr) {
142 unsigned char opcode;
143
144 if (probe_kernel_address(instr, opcode))
145 break;
146
147 instr++;
148
149 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
150 break;
151 }
152 return prefetch;
153}
154
155/*
156 * A protection key fault means that the PKRU value did not allow
157 * access to some PTE. Userspace can figure out what PKRU was
158 * from the XSAVE state, and this function fills out a field in
159 * siginfo so userspace can discover which protection key was set
160 * on the PTE.
161 *
162 * If we get here, we know that the hardware signaled a X86_PF_PK
163 * fault and that there was a VMA once we got in the fault
164 * handler. It does *not* guarantee that the VMA we find here
165 * was the one that we faulted on.
166 *
167 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
168 * 2. T1 : set PKRU to deny access to pkey=4, touches page
169 * 3. T1 : faults...
170 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
171 * 5. T1 : enters fault handler, takes mmap_sem, etc...
172 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
173 * faulted on a pte with its pkey=4.
174 */
175static void fill_sig_info_pkey(int si_signo, int si_code, siginfo_t *info,
176 u32 *pkey)
177{
178 /* This is effectively an #ifdef */
179 if (!boot_cpu_has(X86_FEATURE_OSPKE))
180 return;
181
182 /* Fault not from Protection Keys: nothing to do */
183 if ((si_code != SEGV_PKUERR) || (si_signo != SIGSEGV))
184 return;
185 /*
186 * force_sig_info_fault() is called from a number of
187 * contexts, some of which have a VMA and some of which
188 * do not. The X86_PF_PK handing happens after we have a
189 * valid VMA, so we should never reach this without a
190 * valid VMA.
191 */
192 if (!pkey) {
193 WARN_ONCE(1, "PKU fault with no VMA passed in");
194 info->si_pkey = 0;
195 return;
196 }
197 /*
198 * si_pkey should be thought of as a strong hint, but not
199 * absolutely guranteed to be 100% accurate because of
200 * the race explained above.
201 */
202 info->si_pkey = *pkey;
203}
204
205static void
206force_sig_info_fault(int si_signo, int si_code, unsigned long address,
207 struct task_struct *tsk, u32 *pkey, int fault)
208{
209 unsigned lsb = 0;
210 siginfo_t info;
211
212 info.si_signo = si_signo;
213 info.si_errno = 0;
214 info.si_code = si_code;
215 info.si_addr = (void __user *)address;
216 if (fault & VM_FAULT_HWPOISON_LARGE)
217 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
218 if (fault & VM_FAULT_HWPOISON)
219 lsb = PAGE_SHIFT;
220 info.si_addr_lsb = lsb;
221
222 fill_sig_info_pkey(si_signo, si_code, &info, pkey);
223
224 force_sig_info(si_signo, &info, tsk);
225}
226
227DEFINE_SPINLOCK(pgd_lock);
228LIST_HEAD(pgd_list);
229
230#ifdef CONFIG_X86_32
231static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
232{
233 unsigned index = pgd_index(address);
234 pgd_t *pgd_k;
235 p4d_t *p4d, *p4d_k;
236 pud_t *pud, *pud_k;
237 pmd_t *pmd, *pmd_k;
238
239 pgd += index;
240 pgd_k = init_mm.pgd + index;
241
242 if (!pgd_present(*pgd_k))
243 return NULL;
244
245 /*
246 * set_pgd(pgd, *pgd_k); here would be useless on PAE
247 * and redundant with the set_pmd() on non-PAE. As would
248 * set_p4d/set_pud.
249 */
250 p4d = p4d_offset(pgd, address);
251 p4d_k = p4d_offset(pgd_k, address);
252 if (!p4d_present(*p4d_k))
253 return NULL;
254
255 pud = pud_offset(p4d, address);
256 pud_k = pud_offset(p4d_k, address);
257 if (!pud_present(*pud_k))
258 return NULL;
259
260 pmd = pmd_offset(pud, address);
261 pmd_k = pmd_offset(pud_k, address);
262 if (!pmd_present(*pmd_k))
263 return NULL;
264
265 if (!pmd_present(*pmd))
266 set_pmd(pmd, *pmd_k);
267 else
268 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
269
270 return pmd_k;
271}
272
273void vmalloc_sync_all(void)
274{
275 unsigned long address;
276
277 if (SHARED_KERNEL_PMD)
278 return;
279
280 for (address = VMALLOC_START & PMD_MASK;
281 address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
282 address += PMD_SIZE) {
283 struct page *page;
284
285 spin_lock(&pgd_lock);
286 list_for_each_entry(page, &pgd_list, lru) {
287 spinlock_t *pgt_lock;
288 pmd_t *ret;
289
290 /* the pgt_lock only for Xen */
291 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
292
293 spin_lock(pgt_lock);
294 ret = vmalloc_sync_one(page_address(page), address);
295 spin_unlock(pgt_lock);
296
297 if (!ret)
298 break;
299 }
300 spin_unlock(&pgd_lock);
301 }
302}
303
304/*
305 * 32-bit:
306 *
307 * Handle a fault on the vmalloc or module mapping area
308 */
309static noinline int vmalloc_fault(unsigned long address)
310{
311 unsigned long pgd_paddr;
312 pmd_t *pmd_k;
313 pte_t *pte_k;
314
315 /* Make sure we are in vmalloc area: */
316 if (!(address >= VMALLOC_START && address < VMALLOC_END))
317 return -1;
318
319 WARN_ON_ONCE(in_nmi());
320
321 /*
322 * Synchronize this task's top level page-table
323 * with the 'reference' page table.
324 *
325 * Do _not_ use "current" here. We might be inside
326 * an interrupt in the middle of a task switch..
327 */
328 pgd_paddr = read_cr3_pa();
329 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
330 if (!pmd_k)
331 return -1;
332
333 if (pmd_large(*pmd_k))
334 return 0;
335
336 pte_k = pte_offset_kernel(pmd_k, address);
337 if (!pte_present(*pte_k))
338 return -1;
339
340 return 0;
341}
342NOKPROBE_SYMBOL(vmalloc_fault);
343
344/*
345 * Did it hit the DOS screen memory VA from vm86 mode?
346 */
347static inline void
348check_v8086_mode(struct pt_regs *regs, unsigned long address,
349 struct task_struct *tsk)
350{
351#ifdef CONFIG_VM86
352 unsigned long bit;
353
354 if (!v8086_mode(regs) || !tsk->thread.vm86)
355 return;
356
357 bit = (address - 0xA0000) >> PAGE_SHIFT;
358 if (bit < 32)
359 tsk->thread.vm86->screen_bitmap |= 1 << bit;
360#endif
361}
362
363static bool low_pfn(unsigned long pfn)
364{
365 return pfn < max_low_pfn;
366}
367
368static void dump_pagetable(unsigned long address)
369{
370 pgd_t *base = __va(read_cr3_pa());
371 pgd_t *pgd = &base[pgd_index(address)];
372 p4d_t *p4d;
373 pud_t *pud;
374 pmd_t *pmd;
375 pte_t *pte;
376
377#ifdef CONFIG_X86_PAE
378 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
379 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
380 goto out;
381#define pr_pde pr_cont
382#else
383#define pr_pde pr_info
384#endif
385 p4d = p4d_offset(pgd, address);
386 pud = pud_offset(p4d, address);
387 pmd = pmd_offset(pud, address);
388 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
389#undef pr_pde
390
391 /*
392 * We must not directly access the pte in the highpte
393 * case if the page table is located in highmem.
394 * And let's rather not kmap-atomic the pte, just in case
395 * it's allocated already:
396 */
397 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
398 goto out;
399
400 pte = pte_offset_kernel(pmd, address);
401 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
402out:
403 pr_cont("\n");
404}
405
406#else /* CONFIG_X86_64: */
407
408void vmalloc_sync_all(void)
409{
410 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
411}
412
413/*
414 * 64-bit:
415 *
416 * Handle a fault on the vmalloc area
417 */
418static noinline int vmalloc_fault(unsigned long address)
419{
420 pgd_t *pgd, *pgd_k;
421 p4d_t *p4d, *p4d_k;
422 pud_t *pud;
423 pmd_t *pmd;
424 pte_t *pte;
425
426 /* Make sure we are in vmalloc area: */
427 if (!(address >= VMALLOC_START && address < VMALLOC_END))
428 return -1;
429
430 WARN_ON_ONCE(in_nmi());
431
432 /*
433 * Copy kernel mappings over when needed. This can also
434 * happen within a race in page table update. In the later
435 * case just flush:
436 */
437 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
438 pgd_k = pgd_offset_k(address);
439 if (pgd_none(*pgd_k))
440 return -1;
441
442 if (pgtable_l5_enabled) {
443 if (pgd_none(*pgd)) {
444 set_pgd(pgd, *pgd_k);
445 arch_flush_lazy_mmu_mode();
446 } else {
447 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k));
448 }
449 }
450
451 /* With 4-level paging, copying happens on the p4d level. */
452 p4d = p4d_offset(pgd, address);
453 p4d_k = p4d_offset(pgd_k, address);
454 if (p4d_none(*p4d_k))
455 return -1;
456
457 if (p4d_none(*p4d) && !pgtable_l5_enabled) {
458 set_p4d(p4d, *p4d_k);
459 arch_flush_lazy_mmu_mode();
460 } else {
461 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k));
462 }
463
464 BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);
465
466 pud = pud_offset(p4d, address);
467 if (pud_none(*pud))
468 return -1;
469
470 if (pud_large(*pud))
471 return 0;
472
473 pmd = pmd_offset(pud, address);
474 if (pmd_none(*pmd))
475 return -1;
476
477 if (pmd_large(*pmd))
478 return 0;
479
480 pte = pte_offset_kernel(pmd, address);
481 if (!pte_present(*pte))
482 return -1;
483
484 return 0;
485}
486NOKPROBE_SYMBOL(vmalloc_fault);
487
488#ifdef CONFIG_CPU_SUP_AMD
489static const char errata93_warning[] =
490KERN_ERR
491"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
492"******* Working around it, but it may cause SEGVs or burn power.\n"
493"******* Please consider a BIOS update.\n"
494"******* Disabling USB legacy in the BIOS may also help.\n";
495#endif
496
497/*
498 * No vm86 mode in 64-bit mode:
499 */
500static inline void
501check_v8086_mode(struct pt_regs *regs, unsigned long address,
502 struct task_struct *tsk)
503{
504}
505
506static int bad_address(void *p)
507{
508 unsigned long dummy;
509
510 return probe_kernel_address((unsigned long *)p, dummy);
511}
512
513static void dump_pagetable(unsigned long address)
514{
515 pgd_t *base = __va(read_cr3_pa());
516 pgd_t *pgd = base + pgd_index(address);
517 p4d_t *p4d;
518 pud_t *pud;
519 pmd_t *pmd;
520 pte_t *pte;
521
522 if (bad_address(pgd))
523 goto bad;
524
525 pr_info("PGD %lx ", pgd_val(*pgd));
526
527 if (!pgd_present(*pgd))
528 goto out;
529
530 p4d = p4d_offset(pgd, address);
531 if (bad_address(p4d))
532 goto bad;
533
534 pr_cont("P4D %lx ", p4d_val(*p4d));
535 if (!p4d_present(*p4d) || p4d_large(*p4d))
536 goto out;
537
538 pud = pud_offset(p4d, address);
539 if (bad_address(pud))
540 goto bad;
541
542 pr_cont("PUD %lx ", pud_val(*pud));
543 if (!pud_present(*pud) || pud_large(*pud))
544 goto out;
545
546 pmd = pmd_offset(pud, address);
547 if (bad_address(pmd))
548 goto bad;
549
550 pr_cont("PMD %lx ", pmd_val(*pmd));
551 if (!pmd_present(*pmd) || pmd_large(*pmd))
552 goto out;
553
554 pte = pte_offset_kernel(pmd, address);
555 if (bad_address(pte))
556 goto bad;
557
558 pr_cont("PTE %lx", pte_val(*pte));
559out:
560 pr_cont("\n");
561 return;
562bad:
563 pr_info("BAD\n");
564}
565
566#endif /* CONFIG_X86_64 */
567
568/*
569 * Workaround for K8 erratum #93 & buggy BIOS.
570 *
571 * BIOS SMM functions are required to use a specific workaround
572 * to avoid corruption of the 64bit RIP register on C stepping K8.
573 *
574 * A lot of BIOS that didn't get tested properly miss this.
575 *
576 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
577 * Try to work around it here.
578 *
579 * Note we only handle faults in kernel here.
580 * Does nothing on 32-bit.
581 */
582static int is_errata93(struct pt_regs *regs, unsigned long address)
583{
584#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
585 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
586 || boot_cpu_data.x86 != 0xf)
587 return 0;
588
589 if (address != regs->ip)
590 return 0;
591
592 if ((address >> 32) != 0)
593 return 0;
594
595 address |= 0xffffffffUL << 32;
596 if ((address >= (u64)_stext && address <= (u64)_etext) ||
597 (address >= MODULES_VADDR && address <= MODULES_END)) {
598 printk_once(errata93_warning);
599 regs->ip = address;
600 return 1;
601 }
602#endif
603 return 0;
604}
605
606/*
607 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
608 * to illegal addresses >4GB.
609 *
610 * We catch this in the page fault handler because these addresses
611 * are not reachable. Just detect this case and return. Any code
612 * segment in LDT is compatibility mode.
613 */
614static int is_errata100(struct pt_regs *regs, unsigned long address)
615{
616#ifdef CONFIG_X86_64
617 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
618 return 1;
619#endif
620 return 0;
621}
622
623static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
624{
625#ifdef CONFIG_X86_F00F_BUG
626 unsigned long nr;
627
628 /*
629 * Pentium F0 0F C7 C8 bug workaround:
630 */
631 if (boot_cpu_has_bug(X86_BUG_F00F)) {
632 nr = (address - idt_descr.address) >> 3;
633
634 if (nr == 6) {
635 do_invalid_op(regs, 0);
636 return 1;
637 }
638 }
639#endif
640 return 0;
641}
642
643static const char nx_warning[] = KERN_CRIT
644"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
645static const char smep_warning[] = KERN_CRIT
646"unable to execute userspace code (SMEP?) (uid: %d)\n";
647
648static void
649show_fault_oops(struct pt_regs *regs, unsigned long error_code,
650 unsigned long address)
651{
652 if (!oops_may_print())
653 return;
654
655 if (error_code & X86_PF_INSTR) {
656 unsigned int level;
657 pgd_t *pgd;
658 pte_t *pte;
659
660 pgd = __va(read_cr3_pa());
661 pgd += pgd_index(address);
662
663 pte = lookup_address_in_pgd(pgd, address, &level);
664
665 if (pte && pte_present(*pte) && !pte_exec(*pte))
666 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
667 if (pte && pte_present(*pte) && pte_exec(*pte) &&
668 (pgd_flags(*pgd) & _PAGE_USER) &&
669 (__read_cr4() & X86_CR4_SMEP))
670 printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
671 }
672
673 printk(KERN_ALERT "BUG: unable to handle kernel ");
674 if (address < PAGE_SIZE)
675 printk(KERN_CONT "NULL pointer dereference");
676 else
677 printk(KERN_CONT "paging request");
678
679 printk(KERN_CONT " at %px\n", (void *) address);
680
681 dump_pagetable(address);
682}
683
684static noinline void
685pgtable_bad(struct pt_regs *regs, unsigned long error_code,
686 unsigned long address)
687{
688 struct task_struct *tsk;
689 unsigned long flags;
690 int sig;
691
692 flags = oops_begin();
693 tsk = current;
694 sig = SIGKILL;
695
696 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
697 tsk->comm, address);
698 dump_pagetable(address);
699
700 tsk->thread.cr2 = address;
701 tsk->thread.trap_nr = X86_TRAP_PF;
702 tsk->thread.error_code = error_code;
703
704 if (__die("Bad pagetable", regs, error_code))
705 sig = 0;
706
707 oops_end(flags, regs, sig);
708}
709
710static noinline void
711no_context(struct pt_regs *regs, unsigned long error_code,
712 unsigned long address, int signal, int si_code)
713{
714 struct task_struct *tsk = current;
715 unsigned long flags;
716 int sig;
717
718 /* Are we prepared to handle this kernel fault? */
719 if (fixup_exception(regs, X86_TRAP_PF)) {
720 /*
721 * Any interrupt that takes a fault gets the fixup. This makes
722 * the below recursive fault logic only apply to a faults from
723 * task context.
724 */
725 if (in_interrupt())
726 return;
727
728 /*
729 * Per the above we're !in_interrupt(), aka. task context.
730 *
731 * In this case we need to make sure we're not recursively
732 * faulting through the emulate_vsyscall() logic.
733 */
734 if (current->thread.sig_on_uaccess_err && signal) {
735 tsk->thread.trap_nr = X86_TRAP_PF;
736 tsk->thread.error_code = error_code | X86_PF_USER;
737 tsk->thread.cr2 = address;
738
739 /* XXX: hwpoison faults will set the wrong code. */
740 force_sig_info_fault(signal, si_code, address,
741 tsk, NULL, 0);
742 }
743
744 /*
745 * Barring that, we can do the fixup and be happy.
746 */
747 return;
748 }
749
750#ifdef CONFIG_VMAP_STACK
751 /*
752 * Stack overflow? During boot, we can fault near the initial
753 * stack in the direct map, but that's not an overflow -- check
754 * that we're in vmalloc space to avoid this.
755 */
756 if (is_vmalloc_addr((void *)address) &&
757 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
758 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
759 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
760 /*
761 * We're likely to be running with very little stack space
762 * left. It's plausible that we'd hit this condition but
763 * double-fault even before we get this far, in which case
764 * we're fine: the double-fault handler will deal with it.
765 *
766 * We don't want to make it all the way into the oops code
767 * and then double-fault, though, because we're likely to
768 * break the console driver and lose most of the stack dump.
769 */
770 asm volatile ("movq %[stack], %%rsp\n\t"
771 "call handle_stack_overflow\n\t"
772 "1: jmp 1b"
773 : ASM_CALL_CONSTRAINT
774 : "D" ("kernel stack overflow (page fault)"),
775 "S" (regs), "d" (address),
776 [stack] "rm" (stack));
777 unreachable();
778 }
779#endif
780
781 /*
782 * 32-bit:
783 *
784 * Valid to do another page fault here, because if this fault
785 * had been triggered by is_prefetch fixup_exception would have
786 * handled it.
787 *
788 * 64-bit:
789 *
790 * Hall of shame of CPU/BIOS bugs.
791 */
792 if (is_prefetch(regs, error_code, address))
793 return;
794
795 if (is_errata93(regs, address))
796 return;
797
798 /*
799 * Oops. The kernel tried to access some bad page. We'll have to
800 * terminate things with extreme prejudice:
801 */
802 flags = oops_begin();
803
804 show_fault_oops(regs, error_code, address);
805
806 if (task_stack_end_corrupted(tsk))
807 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
808
809 tsk->thread.cr2 = address;
810 tsk->thread.trap_nr = X86_TRAP_PF;
811 tsk->thread.error_code = error_code;
812
813 sig = SIGKILL;
814 if (__die("Oops", regs, error_code))
815 sig = 0;
816
817 /* Executive summary in case the body of the oops scrolled away */
818 printk(KERN_DEFAULT "CR2: %016lx\n", address);
819
820 oops_end(flags, regs, sig);
821}
822
823/*
824 * Print out info about fatal segfaults, if the show_unhandled_signals
825 * sysctl is set:
826 */
827static inline void
828show_signal_msg(struct pt_regs *regs, unsigned long error_code,
829 unsigned long address, struct task_struct *tsk)
830{
831 if (!unhandled_signal(tsk, SIGSEGV))
832 return;
833
834 if (!printk_ratelimit())
835 return;
836
837 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
838 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
839 tsk->comm, task_pid_nr(tsk), address,
840 (void *)regs->ip, (void *)regs->sp, error_code);
841
842 print_vma_addr(KERN_CONT " in ", regs->ip);
843
844 printk(KERN_CONT "\n");
845}
846
847static void
848__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
849 unsigned long address, u32 *pkey, int si_code)
850{
851 struct task_struct *tsk = current;
852
853 /* User mode accesses just cause a SIGSEGV */
854 if (error_code & X86_PF_USER) {
855 /*
856 * It's possible to have interrupts off here:
857 */
858 local_irq_enable();
859
860 /*
861 * Valid to do another page fault here because this one came
862 * from user space:
863 */
864 if (is_prefetch(regs, error_code, address))
865 return;
866
867 if (is_errata100(regs, address))
868 return;
869
870#ifdef CONFIG_X86_64
871 /*
872 * Instruction fetch faults in the vsyscall page might need
873 * emulation.
874 */
875 if (unlikely((error_code & X86_PF_INSTR) &&
876 ((address & ~0xfff) == VSYSCALL_ADDR))) {
877 if (emulate_vsyscall(regs, address))
878 return;
879 }
880#endif
881
882 /*
883 * To avoid leaking information about the kernel page table
884 * layout, pretend that user-mode accesses to kernel addresses
885 * are always protection faults.
886 */
887 if (address >= TASK_SIZE_MAX)
888 error_code |= X86_PF_PROT;
889
890 if (likely(show_unhandled_signals))
891 show_signal_msg(regs, error_code, address, tsk);
892
893 tsk->thread.cr2 = address;
894 tsk->thread.error_code = error_code;
895 tsk->thread.trap_nr = X86_TRAP_PF;
896
897 force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);
898
899 return;
900 }
901
902 if (is_f00f_bug(regs, address))
903 return;
904
905 no_context(regs, error_code, address, SIGSEGV, si_code);
906}
907
908static noinline void
909bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
910 unsigned long address, u32 *pkey)
911{
912 __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
913}
914
915static void
916__bad_area(struct pt_regs *regs, unsigned long error_code,
917 unsigned long address, struct vm_area_struct *vma, int si_code)
918{
919 struct mm_struct *mm = current->mm;
920 u32 pkey;
921
922 if (vma)
923 pkey = vma_pkey(vma);
924
925 /*
926 * Something tried to access memory that isn't in our memory map..
927 * Fix it, but check if it's kernel or user first..
928 */
929 up_read(&mm->mmap_sem);
930
931 __bad_area_nosemaphore(regs, error_code, address,
932 (vma) ? &pkey : NULL, si_code);
933}
934
935static noinline void
936bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
937{
938 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
939}
940
941static inline bool bad_area_access_from_pkeys(unsigned long error_code,
942 struct vm_area_struct *vma)
943{
944 /* This code is always called on the current mm */
945 bool foreign = false;
946
947 if (!boot_cpu_has(X86_FEATURE_OSPKE))
948 return false;
949 if (error_code & X86_PF_PK)
950 return true;
951 /* this checks permission keys on the VMA: */
952 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
953 (error_code & X86_PF_INSTR), foreign))
954 return true;
955 return false;
956}
957
958static noinline void
959bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
960 unsigned long address, struct vm_area_struct *vma)
961{
962 /*
963 * This OSPKE check is not strictly necessary at runtime.
964 * But, doing it this way allows compiler optimizations
965 * if pkeys are compiled out.
966 */
967 if (bad_area_access_from_pkeys(error_code, vma))
968 __bad_area(regs, error_code, address, vma, SEGV_PKUERR);
969 else
970 __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
971}
972
973static void
974do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
975 u32 *pkey, unsigned int fault)
976{
977 struct task_struct *tsk = current;
978 int code = BUS_ADRERR;
979
980 /* Kernel mode? Handle exceptions or die: */
981 if (!(error_code & X86_PF_USER)) {
982 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
983 return;
984 }
985
986 /* User-space => ok to do another page fault: */
987 if (is_prefetch(regs, error_code, address))
988 return;
989
990 tsk->thread.cr2 = address;
991 tsk->thread.error_code = error_code;
992 tsk->thread.trap_nr = X86_TRAP_PF;
993
994#ifdef CONFIG_MEMORY_FAILURE
995 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
996 printk(KERN_ERR
997 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
998 tsk->comm, tsk->pid, address);
999 code = BUS_MCEERR_AR;
1000 }
1001#endif
1002 force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
1003}
1004
1005static noinline void
1006mm_fault_error(struct pt_regs *regs, unsigned long error_code,
1007 unsigned long address, u32 *pkey, unsigned int fault)
1008{
1009 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
1010 no_context(regs, error_code, address, 0, 0);
1011 return;
1012 }
1013
1014 if (fault & VM_FAULT_OOM) {
1015 /* Kernel mode? Handle exceptions or die: */
1016 if (!(error_code & X86_PF_USER)) {
1017 no_context(regs, error_code, address,
1018 SIGSEGV, SEGV_MAPERR);
1019 return;
1020 }
1021
1022 /*
1023 * We ran out of memory, call the OOM killer, and return the
1024 * userspace (which will retry the fault, or kill us if we got
1025 * oom-killed):
1026 */
1027 pagefault_out_of_memory();
1028 } else {
1029 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1030 VM_FAULT_HWPOISON_LARGE))
1031 do_sigbus(regs, error_code, address, pkey, fault);
1032 else if (fault & VM_FAULT_SIGSEGV)
1033 bad_area_nosemaphore(regs, error_code, address, pkey);
1034 else
1035 BUG();
1036 }
1037}
1038
1039static int spurious_fault_check(unsigned long error_code, pte_t *pte)
1040{
1041 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
1042 return 0;
1043
1044 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
1045 return 0;
1046 /*
1047 * Note: We do not do lazy flushing on protection key
1048 * changes, so no spurious fault will ever set X86_PF_PK.
1049 */
1050 if ((error_code & X86_PF_PK))
1051 return 1;
1052
1053 return 1;
1054}
1055
1056/*
1057 * Handle a spurious fault caused by a stale TLB entry.
1058 *
1059 * This allows us to lazily refresh the TLB when increasing the
1060 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1061 * eagerly is very expensive since that implies doing a full
1062 * cross-processor TLB flush, even if no stale TLB entries exist
1063 * on other processors.
1064 *
1065 * Spurious faults may only occur if the TLB contains an entry with
1066 * fewer permission than the page table entry. Non-present (P = 0)
1067 * and reserved bit (R = 1) faults are never spurious.
1068 *
1069 * There are no security implications to leaving a stale TLB when
1070 * increasing the permissions on a page.
1071 *
1072 * Returns non-zero if a spurious fault was handled, zero otherwise.
1073 *
1074 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1075 * (Optional Invalidation).
1076 */
1077static noinline int
1078spurious_fault(unsigned long error_code, unsigned long address)
1079{
1080 pgd_t *pgd;
1081 p4d_t *p4d;
1082 pud_t *pud;
1083 pmd_t *pmd;
1084 pte_t *pte;
1085 int ret;
1086
1087 /*
1088 * Only writes to RO or instruction fetches from NX may cause
1089 * spurious faults.
1090 *
1091 * These could be from user or supervisor accesses but the TLB
1092 * is only lazily flushed after a kernel mapping protection
1093 * change, so user accesses are not expected to cause spurious
1094 * faults.
1095 */
1096 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1097 error_code != (X86_PF_INSTR | X86_PF_PROT))
1098 return 0;
1099
1100 pgd = init_mm.pgd + pgd_index(address);
1101 if (!pgd_present(*pgd))
1102 return 0;
1103
1104 p4d = p4d_offset(pgd, address);
1105 if (!p4d_present(*p4d))
1106 return 0;
1107
1108 if (p4d_large(*p4d))
1109 return spurious_fault_check(error_code, (pte_t *) p4d);
1110
1111 pud = pud_offset(p4d, address);
1112 if (!pud_present(*pud))
1113 return 0;
1114
1115 if (pud_large(*pud))
1116 return spurious_fault_check(error_code, (pte_t *) pud);
1117
1118 pmd = pmd_offset(pud, address);
1119 if (!pmd_present(*pmd))
1120 return 0;
1121
1122 if (pmd_large(*pmd))
1123 return spurious_fault_check(error_code, (pte_t *) pmd);
1124
1125 pte = pte_offset_kernel(pmd, address);
1126 if (!pte_present(*pte))
1127 return 0;
1128
1129 ret = spurious_fault_check(error_code, pte);
1130 if (!ret)
1131 return 0;
1132
1133 /*
1134 * Make sure we have permissions in PMD.
1135 * If not, then there's a bug in the page tables:
1136 */
1137 ret = spurious_fault_check(error_code, (pte_t *) pmd);
1138 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1139
1140 return ret;
1141}
1142NOKPROBE_SYMBOL(spurious_fault);
1143
1144int show_unhandled_signals = 1;
1145
1146static inline int
1147access_error(unsigned long error_code, struct vm_area_struct *vma)
1148{
1149 /* This is only called for the current mm, so: */
1150 bool foreign = false;
1151
1152 /*
1153 * Read or write was blocked by protection keys. This is
1154 * always an unconditional error and can never result in
1155 * a follow-up action to resolve the fault, like a COW.
1156 */
1157 if (error_code & X86_PF_PK)
1158 return 1;
1159
1160 /*
1161 * Make sure to check the VMA so that we do not perform
1162 * faults just to hit a X86_PF_PK as soon as we fill in a
1163 * page.
1164 */
1165 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1166 (error_code & X86_PF_INSTR), foreign))
1167 return 1;
1168
1169 if (error_code & X86_PF_WRITE) {
1170 /* write, present and write, not present: */
1171 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1172 return 1;
1173 return 0;
1174 }
1175
1176 /* read, present: */
1177 if (unlikely(error_code & X86_PF_PROT))
1178 return 1;
1179
1180 /* read, not present: */
1181 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1182 return 1;
1183
1184 return 0;
1185}
1186
1187static int fault_in_kernel_space(unsigned long address)
1188{
1189 return address >= TASK_SIZE_MAX;
1190}
1191
1192static inline bool smap_violation(int error_code, struct pt_regs *regs)
1193{
1194 if (!IS_ENABLED(CONFIG_X86_SMAP))
1195 return false;
1196
1197 if (!static_cpu_has(X86_FEATURE_SMAP))
1198 return false;
1199
1200 if (error_code & X86_PF_USER)
1201 return false;
1202
1203 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1204 return false;
1205
1206 return true;
1207}
1208
1209/*
1210 * This routine handles page faults. It determines the address,
1211 * and the problem, and then passes it off to one of the appropriate
1212 * routines.
1213 */
1214static noinline void
1215__do_page_fault(struct pt_regs *regs, unsigned long error_code,
1216 unsigned long address)
1217{
1218 struct vm_area_struct *vma;
1219 struct task_struct *tsk;
1220 struct mm_struct *mm;
1221 int fault, major = 0;
1222 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1223 u32 pkey;
1224
1225 tsk = current;
1226 mm = tsk->mm;
1227
1228 prefetchw(&mm->mmap_sem);
1229
1230 if (unlikely(kmmio_fault(regs, address)))
1231 return;
1232
1233 /*
1234 * We fault-in kernel-space virtual memory on-demand. The
1235 * 'reference' page table is init_mm.pgd.
1236 *
1237 * NOTE! We MUST NOT take any locks for this case. We may
1238 * be in an interrupt or a critical region, and should
1239 * only copy the information from the master page table,
1240 * nothing more.
1241 *
1242 * This verifies that the fault happens in kernel space
1243 * (error_code & 4) == 0, and that the fault was not a
1244 * protection error (error_code & 9) == 0.
1245 */
1246 if (unlikely(fault_in_kernel_space(address))) {
1247 if (!(error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1248 if (vmalloc_fault(address) >= 0)
1249 return;
1250 }
1251
1252 /* Can handle a stale RO->RW TLB: */
1253 if (spurious_fault(error_code, address))
1254 return;
1255
1256 /* kprobes don't want to hook the spurious faults: */
1257 if (kprobes_fault(regs))
1258 return;
1259 /*
1260 * Don't take the mm semaphore here. If we fixup a prefetch
1261 * fault we could otherwise deadlock:
1262 */
1263 bad_area_nosemaphore(regs, error_code, address, NULL);
1264
1265 return;
1266 }
1267
1268 /* kprobes don't want to hook the spurious faults: */
1269 if (unlikely(kprobes_fault(regs)))
1270 return;
1271
1272 if (unlikely(error_code & X86_PF_RSVD))
1273 pgtable_bad(regs, error_code, address);
1274
1275 if (unlikely(smap_violation(error_code, regs))) {
1276 bad_area_nosemaphore(regs, error_code, address, NULL);
1277 return;
1278 }
1279
1280 /*
1281 * If we're in an interrupt, have no user context or are running
1282 * in a region with pagefaults disabled then we must not take the fault
1283 */
1284 if (unlikely(faulthandler_disabled() || !mm)) {
1285 bad_area_nosemaphore(regs, error_code, address, NULL);
1286 return;
1287 }
1288
1289 /*
1290 * It's safe to allow irq's after cr2 has been saved and the
1291 * vmalloc fault has been handled.
1292 *
1293 * User-mode registers count as a user access even for any
1294 * potential system fault or CPU buglet:
1295 */
1296 if (user_mode(regs)) {
1297 local_irq_enable();
1298 error_code |= X86_PF_USER;
1299 flags |= FAULT_FLAG_USER;
1300 } else {
1301 if (regs->flags & X86_EFLAGS_IF)
1302 local_irq_enable();
1303 }
1304
1305 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1306
1307 if (error_code & X86_PF_WRITE)
1308 flags |= FAULT_FLAG_WRITE;
1309 if (error_code & X86_PF_INSTR)
1310 flags |= FAULT_FLAG_INSTRUCTION;
1311
1312 /*
1313 * When running in the kernel we expect faults to occur only to
1314 * addresses in user space. All other faults represent errors in
1315 * the kernel and should generate an OOPS. Unfortunately, in the
1316 * case of an erroneous fault occurring in a code path which already
1317 * holds mmap_sem we will deadlock attempting to validate the fault
1318 * against the address space. Luckily the kernel only validly
1319 * references user space from well defined areas of code, which are
1320 * listed in the exceptions table.
1321 *
1322 * As the vast majority of faults will be valid we will only perform
1323 * the source reference check when there is a possibility of a
1324 * deadlock. Attempt to lock the address space, if we cannot we then
1325 * validate the source. If this is invalid we can skip the address
1326 * space check, thus avoiding the deadlock:
1327 */
1328 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1329 if (!(error_code & X86_PF_USER) &&
1330 !search_exception_tables(regs->ip)) {
1331 bad_area_nosemaphore(regs, error_code, address, NULL);
1332 return;
1333 }
1334retry:
1335 down_read(&mm->mmap_sem);
1336 } else {
1337 /*
1338 * The above down_read_trylock() might have succeeded in
1339 * which case we'll have missed the might_sleep() from
1340 * down_read():
1341 */
1342 might_sleep();
1343 }
1344
1345 vma = find_vma(mm, address);
1346 if (unlikely(!vma)) {
1347 bad_area(regs, error_code, address);
1348 return;
1349 }
1350 if (likely(vma->vm_start <= address))
1351 goto good_area;
1352 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1353 bad_area(regs, error_code, address);
1354 return;
1355 }
1356 if (error_code & X86_PF_USER) {
1357 /*
1358 * Accessing the stack below %sp is always a bug.
1359 * The large cushion allows instructions like enter
1360 * and pusha to work. ("enter $65535, $31" pushes
1361 * 32 pointers and then decrements %sp by 65535.)
1362 */
1363 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1364 bad_area(regs, error_code, address);
1365 return;
1366 }
1367 }
1368 if (unlikely(expand_stack(vma, address))) {
1369 bad_area(regs, error_code, address);
1370 return;
1371 }
1372
1373 /*
1374 * Ok, we have a good vm_area for this memory access, so
1375 * we can handle it..
1376 */
1377good_area:
1378 if (unlikely(access_error(error_code, vma))) {
1379 bad_area_access_error(regs, error_code, address, vma);
1380 return;
1381 }
1382
1383 /*
1384 * If for any reason at all we couldn't handle the fault,
1385 * make sure we exit gracefully rather than endlessly redo
1386 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1387 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1388 *
1389 * Note that handle_userfault() may also release and reacquire mmap_sem
1390 * (and not return with VM_FAULT_RETRY), when returning to userland to
1391 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1392 * (potentially after handling any pending signal during the return to
1393 * userland). The return to userland is identified whenever
1394 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1395 * Thus we have to be careful about not touching vma after handling the
1396 * fault, so we read the pkey beforehand.
1397 */
1398 pkey = vma_pkey(vma);
1399 fault = handle_mm_fault(vma, address, flags);
1400 major |= fault & VM_FAULT_MAJOR;
1401
1402 /*
1403 * If we need to retry the mmap_sem has already been released,
1404 * and if there is a fatal signal pending there is no guarantee
1405 * that we made any progress. Handle this case first.
1406 */
1407 if (unlikely(fault & VM_FAULT_RETRY)) {
1408 /* Retry at most once */
1409 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1410 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1411 flags |= FAULT_FLAG_TRIED;
1412 if (!fatal_signal_pending(tsk))
1413 goto retry;
1414 }
1415
1416 /* User mode? Just return to handle the fatal exception */
1417 if (flags & FAULT_FLAG_USER)
1418 return;
1419
1420 /* Not returning to user mode? Handle exceptions or die: */
1421 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1422 return;
1423 }
1424
1425 up_read(&mm->mmap_sem);
1426 if (unlikely(fault & VM_FAULT_ERROR)) {
1427 mm_fault_error(regs, error_code, address, &pkey, fault);
1428 return;
1429 }
1430
1431 /*
1432 * Major/minor page fault accounting. If any of the events
1433 * returned VM_FAULT_MAJOR, we account it as a major fault.
1434 */
1435 if (major) {
1436 tsk->maj_flt++;
1437 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1438 } else {
1439 tsk->min_flt++;
1440 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1441 }
1442
1443 check_v8086_mode(regs, address, tsk);
1444}
1445NOKPROBE_SYMBOL(__do_page_fault);
1446
1447static nokprobe_inline void
1448trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1449 unsigned long error_code)
1450{
1451 if (user_mode(regs))
1452 trace_page_fault_user(address, regs, error_code);
1453 else
1454 trace_page_fault_kernel(address, regs, error_code);
1455}
1456
1457/*
1458 * We must have this function blacklisted from kprobes, tagged with notrace
1459 * and call read_cr2() before calling anything else. To avoid calling any
1460 * kind of tracing machinery before we've observed the CR2 value.
1461 *
1462 * exception_{enter,exit}() contains all sorts of tracepoints.
1463 */
1464dotraplinkage void notrace
1465do_page_fault(struct pt_regs *regs, unsigned long error_code)
1466{
1467 unsigned long address = read_cr2(); /* Get the faulting address */
1468 enum ctx_state prev_state;
1469
1470 prev_state = exception_enter();
1471 if (trace_pagefault_enabled())
1472 trace_page_fault_entries(address, regs, error_code);
1473
1474 __do_page_fault(regs, error_code, address);
1475 exception_exit(prev_state);
1476}
1477NOKPROBE_SYMBOL(do_page_fault);
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
36#define CREATE_TRACE_POINTS
37#include <asm/trace/exceptions.h>
38
39/*
40 * Returns 0 if mmiotrace is disabled, or if the fault is not
41 * handled by mmiotrace:
42 */
43static nokprobe_inline int
44kmmio_fault(struct pt_regs *regs, unsigned long addr)
45{
46 if (unlikely(is_kmmio_active()))
47 if (kmmio_handler(regs, addr) == 1)
48 return -1;
49 return 0;
50}
51
52/*
53 * Prefetch quirks:
54 *
55 * 32-bit mode:
56 *
57 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
58 * Check that here and ignore it. This is AMD erratum #91.
59 *
60 * 64-bit mode:
61 *
62 * Sometimes the CPU reports invalid exceptions on prefetch.
63 * Check that here and ignore it.
64 *
65 * Opcode checker based on code by Richard Brunner.
66 */
67static inline int
68check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
69 unsigned char opcode, int *prefetch)
70{
71 unsigned char instr_hi = opcode & 0xf0;
72 unsigned char instr_lo = opcode & 0x0f;
73
74 switch (instr_hi) {
75 case 0x20:
76 case 0x30:
77 /*
78 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
79 * In X86_64 long mode, the CPU will signal invalid
80 * opcode if some of these prefixes are present so
81 * X86_64 will never get here anyway
82 */
83 return ((instr_lo & 7) == 0x6);
84#ifdef CONFIG_X86_64
85 case 0x40:
86 /*
87 * In 64-bit mode 0x40..0x4F are valid REX prefixes
88 */
89 return (!user_mode(regs) || user_64bit_mode(regs));
90#endif
91 case 0x60:
92 /* 0x64 thru 0x67 are valid prefixes in all modes. */
93 return (instr_lo & 0xC) == 0x4;
94 case 0xF0:
95 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
96 return !instr_lo || (instr_lo>>1) == 1;
97 case 0x00:
98 /* Prefetch instruction is 0x0F0D or 0x0F18 */
99 if (get_kernel_nofault(opcode, instr))
100 return 0;
101
102 *prefetch = (instr_lo == 0xF) &&
103 (opcode == 0x0D || opcode == 0x18);
104 return 0;
105 default:
106 return 0;
107 }
108}
109
110static bool is_amd_k8_pre_npt(void)
111{
112 struct cpuinfo_x86 *c = &boot_cpu_data;
113
114 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
115 c->x86_vendor == X86_VENDOR_AMD &&
116 c->x86 == 0xf && c->x86_model < 0x40);
117}
118
119static int
120is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
121{
122 unsigned char *max_instr;
123 unsigned char *instr;
124 int prefetch = 0;
125
126 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
127 if (!is_amd_k8_pre_npt())
128 return 0;
129
130 /*
131 * If it was a exec (instruction fetch) fault on NX page, then
132 * do not ignore the fault:
133 */
134 if (error_code & X86_PF_INSTR)
135 return 0;
136
137 instr = (void *)convert_ip_to_linear(current, regs);
138 max_instr = instr + 15;
139
140 /*
141 * This code has historically always bailed out if IP points to a
142 * not-present page (e.g. due to a race). No one has ever
143 * complained about this.
144 */
145 pagefault_disable();
146
147 while (instr < max_instr) {
148 unsigned char opcode;
149
150 if (user_mode(regs)) {
151 if (get_user(opcode, instr))
152 break;
153 } else {
154 if (get_kernel_nofault(opcode, instr))
155 break;
156 }
157
158 instr++;
159
160 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
161 break;
162 }
163
164 pagefault_enable();
165 return prefetch;
166}
167
168DEFINE_SPINLOCK(pgd_lock);
169LIST_HEAD(pgd_list);
170
171#ifdef CONFIG_X86_32
172static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
173{
174 unsigned index = pgd_index(address);
175 pgd_t *pgd_k;
176 p4d_t *p4d, *p4d_k;
177 pud_t *pud, *pud_k;
178 pmd_t *pmd, *pmd_k;
179
180 pgd += index;
181 pgd_k = init_mm.pgd + index;
182
183 if (!pgd_present(*pgd_k))
184 return NULL;
185
186 /*
187 * set_pgd(pgd, *pgd_k); here would be useless on PAE
188 * and redundant with the set_pmd() on non-PAE. As would
189 * set_p4d/set_pud.
190 */
191 p4d = p4d_offset(pgd, address);
192 p4d_k = p4d_offset(pgd_k, address);
193 if (!p4d_present(*p4d_k))
194 return NULL;
195
196 pud = pud_offset(p4d, address);
197 pud_k = pud_offset(p4d_k, address);
198 if (!pud_present(*pud_k))
199 return NULL;
200
201 pmd = pmd_offset(pud, address);
202 pmd_k = pmd_offset(pud_k, address);
203
204 if (pmd_present(*pmd) != pmd_present(*pmd_k))
205 set_pmd(pmd, *pmd_k);
206
207 if (!pmd_present(*pmd_k))
208 return NULL;
209 else
210 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
211
212 return pmd_k;
213}
214
215/*
216 * Handle a fault on the vmalloc or module mapping area
217 *
218 * This is needed because there is a race condition between the time
219 * when the vmalloc mapping code updates the PMD to the point in time
220 * where it synchronizes this update with the other page-tables in the
221 * system.
222 *
223 * In this race window another thread/CPU can map an area on the same
224 * PMD, finds it already present and does not synchronize it with the
225 * rest of the system yet. As a result v[mz]alloc might return areas
226 * which are not mapped in every page-table in the system, causing an
227 * unhandled page-fault when they are accessed.
228 */
229static noinline int vmalloc_fault(unsigned long address)
230{
231 unsigned long pgd_paddr;
232 pmd_t *pmd_k;
233 pte_t *pte_k;
234
235 /* Make sure we are in vmalloc area: */
236 if (!(address >= VMALLOC_START && address < VMALLOC_END))
237 return -1;
238
239 /*
240 * Synchronize this task's top level page-table
241 * with the 'reference' page table.
242 *
243 * Do _not_ use "current" here. We might be inside
244 * an interrupt in the middle of a task switch..
245 */
246 pgd_paddr = read_cr3_pa();
247 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
248 if (!pmd_k)
249 return -1;
250
251 if (pmd_large(*pmd_k))
252 return 0;
253
254 pte_k = pte_offset_kernel(pmd_k, address);
255 if (!pte_present(*pte_k))
256 return -1;
257
258 return 0;
259}
260NOKPROBE_SYMBOL(vmalloc_fault);
261
262void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
263{
264 unsigned long addr;
265
266 for (addr = start & PMD_MASK;
267 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
268 addr += PMD_SIZE) {
269 struct page *page;
270
271 spin_lock(&pgd_lock);
272 list_for_each_entry(page, &pgd_list, lru) {
273 spinlock_t *pgt_lock;
274
275 /* the pgt_lock only for Xen */
276 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
277
278 spin_lock(pgt_lock);
279 vmalloc_sync_one(page_address(page), addr);
280 spin_unlock(pgt_lock);
281 }
282 spin_unlock(&pgd_lock);
283 }
284}
285
286static bool low_pfn(unsigned long pfn)
287{
288 return pfn < max_low_pfn;
289}
290
291static void dump_pagetable(unsigned long address)
292{
293 pgd_t *base = __va(read_cr3_pa());
294 pgd_t *pgd = &base[pgd_index(address)];
295 p4d_t *p4d;
296 pud_t *pud;
297 pmd_t *pmd;
298 pte_t *pte;
299
300#ifdef CONFIG_X86_PAE
301 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
302 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
303 goto out;
304#define pr_pde pr_cont
305#else
306#define pr_pde pr_info
307#endif
308 p4d = p4d_offset(pgd, address);
309 pud = pud_offset(p4d, address);
310 pmd = pmd_offset(pud, address);
311 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
312#undef pr_pde
313
314 /*
315 * We must not directly access the pte in the highpte
316 * case if the page table is located in highmem.
317 * And let's rather not kmap-atomic the pte, just in case
318 * it's allocated already:
319 */
320 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
321 goto out;
322
323 pte = pte_offset_kernel(pmd, address);
324 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
325out:
326 pr_cont("\n");
327}
328
329#else /* CONFIG_X86_64: */
330
331#ifdef CONFIG_CPU_SUP_AMD
332static const char errata93_warning[] =
333KERN_ERR
334"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
335"******* Working around it, but it may cause SEGVs or burn power.\n"
336"******* Please consider a BIOS update.\n"
337"******* Disabling USB legacy in the BIOS may also help.\n";
338#endif
339
340static int bad_address(void *p)
341{
342 unsigned long dummy;
343
344 return get_kernel_nofault(dummy, (unsigned long *)p);
345}
346
347static void dump_pagetable(unsigned long address)
348{
349 pgd_t *base = __va(read_cr3_pa());
350 pgd_t *pgd = base + pgd_index(address);
351 p4d_t *p4d;
352 pud_t *pud;
353 pmd_t *pmd;
354 pte_t *pte;
355
356 if (bad_address(pgd))
357 goto bad;
358
359 pr_info("PGD %lx ", pgd_val(*pgd));
360
361 if (!pgd_present(*pgd))
362 goto out;
363
364 p4d = p4d_offset(pgd, address);
365 if (bad_address(p4d))
366 goto bad;
367
368 pr_cont("P4D %lx ", p4d_val(*p4d));
369 if (!p4d_present(*p4d) || p4d_large(*p4d))
370 goto out;
371
372 pud = pud_offset(p4d, address);
373 if (bad_address(pud))
374 goto bad;
375
376 pr_cont("PUD %lx ", pud_val(*pud));
377 if (!pud_present(*pud) || pud_large(*pud))
378 goto out;
379
380 pmd = pmd_offset(pud, address);
381 if (bad_address(pmd))
382 goto bad;
383
384 pr_cont("PMD %lx ", pmd_val(*pmd));
385 if (!pmd_present(*pmd) || pmd_large(*pmd))
386 goto out;
387
388 pte = pte_offset_kernel(pmd, address);
389 if (bad_address(pte))
390 goto bad;
391
392 pr_cont("PTE %lx", pte_val(*pte));
393out:
394 pr_cont("\n");
395 return;
396bad:
397 pr_info("BAD\n");
398}
399
400#endif /* CONFIG_X86_64 */
401
402/*
403 * Workaround for K8 erratum #93 & buggy BIOS.
404 *
405 * BIOS SMM functions are required to use a specific workaround
406 * to avoid corruption of the 64bit RIP register on C stepping K8.
407 *
408 * A lot of BIOS that didn't get tested properly miss this.
409 *
410 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
411 * Try to work around it here.
412 *
413 * Note we only handle faults in kernel here.
414 * Does nothing on 32-bit.
415 */
416static int is_errata93(struct pt_regs *regs, unsigned long address)
417{
418#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
419 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
420 || boot_cpu_data.x86 != 0xf)
421 return 0;
422
423 if (user_mode(regs))
424 return 0;
425
426 if (address != regs->ip)
427 return 0;
428
429 if ((address >> 32) != 0)
430 return 0;
431
432 address |= 0xffffffffUL << 32;
433 if ((address >= (u64)_stext && address <= (u64)_etext) ||
434 (address >= MODULES_VADDR && address <= MODULES_END)) {
435 printk_once(errata93_warning);
436 regs->ip = address;
437 return 1;
438 }
439#endif
440 return 0;
441}
442
443/*
444 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
445 * to illegal addresses >4GB.
446 *
447 * We catch this in the page fault handler because these addresses
448 * are not reachable. Just detect this case and return. Any code
449 * segment in LDT is compatibility mode.
450 */
451static int is_errata100(struct pt_regs *regs, unsigned long address)
452{
453#ifdef CONFIG_X86_64
454 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
455 return 1;
456#endif
457 return 0;
458}
459
460/* Pentium F0 0F C7 C8 bug workaround: */
461static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
462 unsigned long address)
463{
464#ifdef CONFIG_X86_F00F_BUG
465 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
466 idt_is_f00f_address(address)) {
467 handle_invalid_op(regs);
468 return 1;
469 }
470#endif
471 return 0;
472}
473
474static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
475{
476 u32 offset = (index >> 3) * sizeof(struct desc_struct);
477 unsigned long addr;
478 struct ldttss_desc desc;
479
480 if (index == 0) {
481 pr_alert("%s: NULL\n", name);
482 return;
483 }
484
485 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
486 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
487 return;
488 }
489
490 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
491 sizeof(struct ldttss_desc))) {
492 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
493 name, index);
494 return;
495 }
496
497 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
498#ifdef CONFIG_X86_64
499 addr |= ((u64)desc.base3 << 32);
500#endif
501 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
502 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
503}
504
505static void
506show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
507{
508 if (!oops_may_print())
509 return;
510
511 if (error_code & X86_PF_INSTR) {
512 unsigned int level;
513 pgd_t *pgd;
514 pte_t *pte;
515
516 pgd = __va(read_cr3_pa());
517 pgd += pgd_index(address);
518
519 pte = lookup_address_in_pgd(pgd, address, &level);
520
521 if (pte && pte_present(*pte) && !pte_exec(*pte))
522 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
523 from_kuid(&init_user_ns, current_uid()));
524 if (pte && pte_present(*pte) && pte_exec(*pte) &&
525 (pgd_flags(*pgd) & _PAGE_USER) &&
526 (__read_cr4() & X86_CR4_SMEP))
527 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
528 from_kuid(&init_user_ns, current_uid()));
529 }
530
531 if (address < PAGE_SIZE && !user_mode(regs))
532 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
533 (void *)address);
534 else
535 pr_alert("BUG: unable to handle page fault for address: %px\n",
536 (void *)address);
537
538 pr_alert("#PF: %s %s in %s mode\n",
539 (error_code & X86_PF_USER) ? "user" : "supervisor",
540 (error_code & X86_PF_INSTR) ? "instruction fetch" :
541 (error_code & X86_PF_WRITE) ? "write access" :
542 "read access",
543 user_mode(regs) ? "user" : "kernel");
544 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
545 !(error_code & X86_PF_PROT) ? "not-present page" :
546 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
547 (error_code & X86_PF_PK) ? "protection keys violation" :
548 "permissions violation");
549
550 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
551 struct desc_ptr idt, gdt;
552 u16 ldtr, tr;
553
554 /*
555 * This can happen for quite a few reasons. The more obvious
556 * ones are faults accessing the GDT, or LDT. Perhaps
557 * surprisingly, if the CPU tries to deliver a benign or
558 * contributory exception from user code and gets a page fault
559 * during delivery, the page fault can be delivered as though
560 * it originated directly from user code. This could happen
561 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
562 * kernel or IST stack.
563 */
564 store_idt(&idt);
565
566 /* Usable even on Xen PV -- it's just slow. */
567 native_store_gdt(&gdt);
568
569 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
570 idt.address, idt.size, gdt.address, gdt.size);
571
572 store_ldt(ldtr);
573 show_ldttss(&gdt, "LDTR", ldtr);
574
575 store_tr(tr);
576 show_ldttss(&gdt, "TR", tr);
577 }
578
579 dump_pagetable(address);
580}
581
582static noinline void
583pgtable_bad(struct pt_regs *regs, unsigned long error_code,
584 unsigned long address)
585{
586 struct task_struct *tsk;
587 unsigned long flags;
588 int sig;
589
590 flags = oops_begin();
591 tsk = current;
592 sig = SIGKILL;
593
594 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
595 tsk->comm, address);
596 dump_pagetable(address);
597
598 if (__die("Bad pagetable", regs, error_code))
599 sig = 0;
600
601 oops_end(flags, regs, sig);
602}
603
604static void sanitize_error_code(unsigned long address,
605 unsigned long *error_code)
606{
607 /*
608 * To avoid leaking information about the kernel page
609 * table layout, pretend that user-mode accesses to
610 * kernel addresses are always protection faults.
611 *
612 * NB: This means that failed vsyscalls with vsyscall=none
613 * will have the PROT bit. This doesn't leak any
614 * information and does not appear to cause any problems.
615 */
616 if (address >= TASK_SIZE_MAX)
617 *error_code |= X86_PF_PROT;
618}
619
620static void set_signal_archinfo(unsigned long address,
621 unsigned long error_code)
622{
623 struct task_struct *tsk = current;
624
625 tsk->thread.trap_nr = X86_TRAP_PF;
626 tsk->thread.error_code = error_code | X86_PF_USER;
627 tsk->thread.cr2 = address;
628}
629
630static noinline void
631page_fault_oops(struct pt_regs *regs, unsigned long error_code,
632 unsigned long address)
633{
634 unsigned long flags;
635 int sig;
636
637 if (user_mode(regs)) {
638 /*
639 * Implicit kernel access from user mode? Skip the stack
640 * overflow and EFI special cases.
641 */
642 goto oops;
643 }
644
645#ifdef CONFIG_VMAP_STACK
646 /*
647 * Stack overflow? During boot, we can fault near the initial
648 * stack in the direct map, but that's not an overflow -- check
649 * that we're in vmalloc space to avoid this.
650 */
651 if (is_vmalloc_addr((void *)address) &&
652 (((unsigned long)current->stack - 1 - address < PAGE_SIZE) ||
653 address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) {
654 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
655 /*
656 * We're likely to be running with very little stack space
657 * left. It's plausible that we'd hit this condition but
658 * double-fault even before we get this far, in which case
659 * we're fine: the double-fault handler will deal with it.
660 *
661 * We don't want to make it all the way into the oops code
662 * and then double-fault, though, because we're likely to
663 * break the console driver and lose most of the stack dump.
664 */
665 asm volatile ("movq %[stack], %%rsp\n\t"
666 "call handle_stack_overflow\n\t"
667 "1: jmp 1b"
668 : ASM_CALL_CONSTRAINT
669 : "D" ("kernel stack overflow (page fault)"),
670 "S" (regs), "d" (address),
671 [stack] "rm" (stack));
672 unreachable();
673 }
674#endif
675
676 /*
677 * Buggy firmware could access regions which might page fault. If
678 * this happens, EFI has a special OOPS path that will try to
679 * avoid hanging the system.
680 */
681 if (IS_ENABLED(CONFIG_EFI))
682 efi_crash_gracefully_on_page_fault(address);
683
684 /* Only not-present faults should be handled by KFENCE. */
685 if (!(error_code & X86_PF_PROT) &&
686 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
687 return;
688
689oops:
690 /*
691 * Oops. The kernel tried to access some bad page. We'll have to
692 * terminate things with extreme prejudice:
693 */
694 flags = oops_begin();
695
696 show_fault_oops(regs, error_code, address);
697
698 if (task_stack_end_corrupted(current))
699 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
700
701 sig = SIGKILL;
702 if (__die("Oops", regs, error_code))
703 sig = 0;
704
705 /* Executive summary in case the body of the oops scrolled away */
706 printk(KERN_DEFAULT "CR2: %016lx\n", address);
707
708 oops_end(flags, regs, sig);
709}
710
711static noinline void
712kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
713 unsigned long address, int signal, int si_code,
714 u32 pkey)
715{
716 WARN_ON_ONCE(user_mode(regs));
717
718 /* Are we prepared to handle this kernel fault? */
719 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
720 /*
721 * Any interrupt that takes a fault gets the fixup. This makes
722 * the below recursive fault logic only apply to a faults from
723 * task context.
724 */
725 if (in_interrupt())
726 return;
727
728 /*
729 * Per the above we're !in_interrupt(), aka. task context.
730 *
731 * In this case we need to make sure we're not recursively
732 * faulting through the emulate_vsyscall() logic.
733 */
734 if (current->thread.sig_on_uaccess_err && signal) {
735 sanitize_error_code(address, &error_code);
736
737 set_signal_archinfo(address, error_code);
738
739 if (si_code == SEGV_PKUERR) {
740 force_sig_pkuerr((void __user *)address, pkey);
741 } else {
742 /* XXX: hwpoison faults will set the wrong code. */
743 force_sig_fault(signal, si_code, (void __user *)address);
744 }
745 }
746
747 /*
748 * Barring that, we can do the fixup and be happy.
749 */
750 return;
751 }
752
753 /*
754 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
755 * instruction.
756 */
757 if (is_prefetch(regs, error_code, address))
758 return;
759
760 page_fault_oops(regs, error_code, address);
761}
762
763/*
764 * Print out info about fatal segfaults, if the show_unhandled_signals
765 * sysctl is set:
766 */
767static inline void
768show_signal_msg(struct pt_regs *regs, unsigned long error_code,
769 unsigned long address, struct task_struct *tsk)
770{
771 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
772
773 if (!unhandled_signal(tsk, SIGSEGV))
774 return;
775
776 if (!printk_ratelimit())
777 return;
778
779 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
780 loglvl, tsk->comm, task_pid_nr(tsk), address,
781 (void *)regs->ip, (void *)regs->sp, error_code);
782
783 print_vma_addr(KERN_CONT " in ", regs->ip);
784
785 printk(KERN_CONT "\n");
786
787 show_opcodes(regs, loglvl);
788}
789
790/*
791 * The (legacy) vsyscall page is the long page in the kernel portion
792 * of the address space that has user-accessible permissions.
793 */
794static bool is_vsyscall_vaddr(unsigned long vaddr)
795{
796 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
797}
798
799static void
800__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
801 unsigned long address, u32 pkey, int si_code)
802{
803 struct task_struct *tsk = current;
804
805 if (!user_mode(regs)) {
806 kernelmode_fixup_or_oops(regs, error_code, address,
807 SIGSEGV, si_code, pkey);
808 return;
809 }
810
811 if (!(error_code & X86_PF_USER)) {
812 /* Implicit user access to kernel memory -- just oops */
813 page_fault_oops(regs, error_code, address);
814 return;
815 }
816
817 /*
818 * User mode accesses just cause a SIGSEGV.
819 * It's possible to have interrupts off here:
820 */
821 local_irq_enable();
822
823 /*
824 * Valid to do another page fault here because this one came
825 * from user space:
826 */
827 if (is_prefetch(regs, error_code, address))
828 return;
829
830 if (is_errata100(regs, address))
831 return;
832
833 sanitize_error_code(address, &error_code);
834
835 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
836 return;
837
838 if (likely(show_unhandled_signals))
839 show_signal_msg(regs, error_code, address, tsk);
840
841 set_signal_archinfo(address, error_code);
842
843 if (si_code == SEGV_PKUERR)
844 force_sig_pkuerr((void __user *)address, pkey);
845 else
846 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
847
848 local_irq_disable();
849}
850
851static noinline void
852bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
853 unsigned long address)
854{
855 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
856}
857
858static void
859__bad_area(struct pt_regs *regs, unsigned long error_code,
860 unsigned long address, u32 pkey, int si_code)
861{
862 struct mm_struct *mm = current->mm;
863 /*
864 * Something tried to access memory that isn't in our memory map..
865 * Fix it, but check if it's kernel or user first..
866 */
867 mmap_read_unlock(mm);
868
869 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
870}
871
872static noinline void
873bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
874{
875 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
876}
877
878static inline bool bad_area_access_from_pkeys(unsigned long error_code,
879 struct vm_area_struct *vma)
880{
881 /* This code is always called on the current mm */
882 bool foreign = false;
883
884 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
885 return false;
886 if (error_code & X86_PF_PK)
887 return true;
888 /* this checks permission keys on the VMA: */
889 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
890 (error_code & X86_PF_INSTR), foreign))
891 return true;
892 return false;
893}
894
895static noinline void
896bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
897 unsigned long address, struct vm_area_struct *vma)
898{
899 /*
900 * This OSPKE check is not strictly necessary at runtime.
901 * But, doing it this way allows compiler optimizations
902 * if pkeys are compiled out.
903 */
904 if (bad_area_access_from_pkeys(error_code, vma)) {
905 /*
906 * A protection key fault means that the PKRU value did not allow
907 * access to some PTE. Userspace can figure out what PKRU was
908 * from the XSAVE state. This function captures the pkey from
909 * the vma and passes it to userspace so userspace can discover
910 * which protection key was set on the PTE.
911 *
912 * If we get here, we know that the hardware signaled a X86_PF_PK
913 * fault and that there was a VMA once we got in the fault
914 * handler. It does *not* guarantee that the VMA we find here
915 * was the one that we faulted on.
916 *
917 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
918 * 2. T1 : set PKRU to deny access to pkey=4, touches page
919 * 3. T1 : faults...
920 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
921 * 5. T1 : enters fault handler, takes mmap_lock, etc...
922 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
923 * faulted on a pte with its pkey=4.
924 */
925 u32 pkey = vma_pkey(vma);
926
927 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
928 } else {
929 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
930 }
931}
932
933static void
934do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
935 vm_fault_t fault)
936{
937 /* Kernel mode? Handle exceptions or die: */
938 if (!user_mode(regs)) {
939 kernelmode_fixup_or_oops(regs, error_code, address,
940 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
941 return;
942 }
943
944 /* User-space => ok to do another page fault: */
945 if (is_prefetch(regs, error_code, address))
946 return;
947
948 sanitize_error_code(address, &error_code);
949
950 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
951 return;
952
953 set_signal_archinfo(address, error_code);
954
955#ifdef CONFIG_MEMORY_FAILURE
956 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
957 struct task_struct *tsk = current;
958 unsigned lsb = 0;
959
960 pr_err(
961 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
962 tsk->comm, tsk->pid, address);
963 if (fault & VM_FAULT_HWPOISON_LARGE)
964 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
965 if (fault & VM_FAULT_HWPOISON)
966 lsb = PAGE_SHIFT;
967 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
968 return;
969 }
970#endif
971 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
972}
973
974static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
975{
976 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
977 return 0;
978
979 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
980 return 0;
981
982 return 1;
983}
984
985/*
986 * Handle a spurious fault caused by a stale TLB entry.
987 *
988 * This allows us to lazily refresh the TLB when increasing the
989 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
990 * eagerly is very expensive since that implies doing a full
991 * cross-processor TLB flush, even if no stale TLB entries exist
992 * on other processors.
993 *
994 * Spurious faults may only occur if the TLB contains an entry with
995 * fewer permission than the page table entry. Non-present (P = 0)
996 * and reserved bit (R = 1) faults are never spurious.
997 *
998 * There are no security implications to leaving a stale TLB when
999 * increasing the permissions on a page.
1000 *
1001 * Returns non-zero if a spurious fault was handled, zero otherwise.
1002 *
1003 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1004 * (Optional Invalidation).
1005 */
1006static noinline int
1007spurious_kernel_fault(unsigned long error_code, unsigned long address)
1008{
1009 pgd_t *pgd;
1010 p4d_t *p4d;
1011 pud_t *pud;
1012 pmd_t *pmd;
1013 pte_t *pte;
1014 int ret;
1015
1016 /*
1017 * Only writes to RO or instruction fetches from NX may cause
1018 * spurious faults.
1019 *
1020 * These could be from user or supervisor accesses but the TLB
1021 * is only lazily flushed after a kernel mapping protection
1022 * change, so user accesses are not expected to cause spurious
1023 * faults.
1024 */
1025 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1026 error_code != (X86_PF_INSTR | X86_PF_PROT))
1027 return 0;
1028
1029 pgd = init_mm.pgd + pgd_index(address);
1030 if (!pgd_present(*pgd))
1031 return 0;
1032
1033 p4d = p4d_offset(pgd, address);
1034 if (!p4d_present(*p4d))
1035 return 0;
1036
1037 if (p4d_large(*p4d))
1038 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1039
1040 pud = pud_offset(p4d, address);
1041 if (!pud_present(*pud))
1042 return 0;
1043
1044 if (pud_large(*pud))
1045 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1046
1047 pmd = pmd_offset(pud, address);
1048 if (!pmd_present(*pmd))
1049 return 0;
1050
1051 if (pmd_large(*pmd))
1052 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1053
1054 pte = pte_offset_kernel(pmd, address);
1055 if (!pte_present(*pte))
1056 return 0;
1057
1058 ret = spurious_kernel_fault_check(error_code, pte);
1059 if (!ret)
1060 return 0;
1061
1062 /*
1063 * Make sure we have permissions in PMD.
1064 * If not, then there's a bug in the page tables:
1065 */
1066 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1067 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1068
1069 return ret;
1070}
1071NOKPROBE_SYMBOL(spurious_kernel_fault);
1072
1073int show_unhandled_signals = 1;
1074
1075static inline int
1076access_error(unsigned long error_code, struct vm_area_struct *vma)
1077{
1078 /* This is only called for the current mm, so: */
1079 bool foreign = false;
1080
1081 /*
1082 * Read or write was blocked by protection keys. This is
1083 * always an unconditional error and can never result in
1084 * a follow-up action to resolve the fault, like a COW.
1085 */
1086 if (error_code & X86_PF_PK)
1087 return 1;
1088
1089 /*
1090 * SGX hardware blocked the access. This usually happens
1091 * when the enclave memory contents have been destroyed, like
1092 * after a suspend/resume cycle. In any case, the kernel can't
1093 * fix the cause of the fault. Handle the fault as an access
1094 * error even in cases where no actual access violation
1095 * occurred. This allows userspace to rebuild the enclave in
1096 * response to the signal.
1097 */
1098 if (unlikely(error_code & X86_PF_SGX))
1099 return 1;
1100
1101 /*
1102 * Make sure to check the VMA so that we do not perform
1103 * faults just to hit a X86_PF_PK as soon as we fill in a
1104 * page.
1105 */
1106 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1107 (error_code & X86_PF_INSTR), foreign))
1108 return 1;
1109
1110 if (error_code & X86_PF_WRITE) {
1111 /* write, present and write, not present: */
1112 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1113 return 1;
1114 return 0;
1115 }
1116
1117 /* read, present: */
1118 if (unlikely(error_code & X86_PF_PROT))
1119 return 1;
1120
1121 /* read, not present: */
1122 if (unlikely(!vma_is_accessible(vma)))
1123 return 1;
1124
1125 return 0;
1126}
1127
1128bool fault_in_kernel_space(unsigned long address)
1129{
1130 /*
1131 * On 64-bit systems, the vsyscall page is at an address above
1132 * TASK_SIZE_MAX, but is not considered part of the kernel
1133 * address space.
1134 */
1135 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1136 return false;
1137
1138 return address >= TASK_SIZE_MAX;
1139}
1140
1141/*
1142 * Called for all faults where 'address' is part of the kernel address
1143 * space. Might get called for faults that originate from *code* that
1144 * ran in userspace or the kernel.
1145 */
1146static void
1147do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1148 unsigned long address)
1149{
1150 /*
1151 * Protection keys exceptions only happen on user pages. We
1152 * have no user pages in the kernel portion of the address
1153 * space, so do not expect them here.
1154 */
1155 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1156
1157#ifdef CONFIG_X86_32
1158 /*
1159 * We can fault-in kernel-space virtual memory on-demand. The
1160 * 'reference' page table is init_mm.pgd.
1161 *
1162 * NOTE! We MUST NOT take any locks for this case. We may
1163 * be in an interrupt or a critical region, and should
1164 * only copy the information from the master page table,
1165 * nothing more.
1166 *
1167 * Before doing this on-demand faulting, ensure that the
1168 * fault is not any of the following:
1169 * 1. A fault on a PTE with a reserved bit set.
1170 * 2. A fault caused by a user-mode access. (Do not demand-
1171 * fault kernel memory due to user-mode accesses).
1172 * 3. A fault caused by a page-level protection violation.
1173 * (A demand fault would be on a non-present page which
1174 * would have X86_PF_PROT==0).
1175 *
1176 * This is only needed to close a race condition on x86-32 in
1177 * the vmalloc mapping/unmapping code. See the comment above
1178 * vmalloc_fault() for details. On x86-64 the race does not
1179 * exist as the vmalloc mappings don't need to be synchronized
1180 * there.
1181 */
1182 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1183 if (vmalloc_fault(address) >= 0)
1184 return;
1185 }
1186#endif
1187
1188 if (is_f00f_bug(regs, hw_error_code, address))
1189 return;
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 (WARN_ON_ONCE(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/*
1212 * Handle faults in the user portion of the address space. Nothing in here
1213 * should check X86_PF_USER without a specific justification: for almost
1214 * all purposes, we should treat a normal kernel access to user memory
1215 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1216 * The one exception is AC flag handling, which is, per the x86
1217 * architecture, special for WRUSS.
1218 */
1219static inline
1220void do_user_addr_fault(struct pt_regs *regs,
1221 unsigned long error_code,
1222 unsigned long address)
1223{
1224 struct vm_area_struct *vma;
1225 struct task_struct *tsk;
1226 struct mm_struct *mm;
1227 vm_fault_t fault;
1228 unsigned int flags = FAULT_FLAG_DEFAULT;
1229
1230 tsk = current;
1231 mm = tsk->mm;
1232
1233 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1234 /*
1235 * Whoops, this is kernel mode code trying to execute from
1236 * user memory. Unless this is AMD erratum #93, which
1237 * corrupts RIP such that it looks like a user address,
1238 * this is unrecoverable. Don't even try to look up the
1239 * VMA or look for extable entries.
1240 */
1241 if (is_errata93(regs, address))
1242 return;
1243
1244 page_fault_oops(regs, error_code, address);
1245 return;
1246 }
1247
1248 /* kprobes don't want to hook the spurious faults: */
1249 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1250 return;
1251
1252 /*
1253 * Reserved bits are never expected to be set on
1254 * entries in the user portion of the page tables.
1255 */
1256 if (unlikely(error_code & X86_PF_RSVD))
1257 pgtable_bad(regs, error_code, address);
1258
1259 /*
1260 * If SMAP is on, check for invalid kernel (supervisor) access to user
1261 * pages in the user address space. The odd case here is WRUSS,
1262 * which, according to the preliminary documentation, does not respect
1263 * SMAP and will have the USER bit set so, in all cases, SMAP
1264 * enforcement appears to be consistent with the USER bit.
1265 */
1266 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1267 !(error_code & X86_PF_USER) &&
1268 !(regs->flags & X86_EFLAGS_AC))) {
1269 /*
1270 * No extable entry here. This was a kernel access to an
1271 * invalid pointer. get_kernel_nofault() will not get here.
1272 */
1273 page_fault_oops(regs, error_code, address);
1274 return;
1275 }
1276
1277 /*
1278 * If we're in an interrupt, have no user context or are running
1279 * in a region with pagefaults disabled then we must not take the fault
1280 */
1281 if (unlikely(faulthandler_disabled() || !mm)) {
1282 bad_area_nosemaphore(regs, error_code, address);
1283 return;
1284 }
1285
1286 /*
1287 * It's safe to allow irq's after cr2 has been saved and the
1288 * vmalloc fault has been handled.
1289 *
1290 * User-mode registers count as a user access even for any
1291 * potential system fault or CPU buglet:
1292 */
1293 if (user_mode(regs)) {
1294 local_irq_enable();
1295 flags |= FAULT_FLAG_USER;
1296 } else {
1297 if (regs->flags & X86_EFLAGS_IF)
1298 local_irq_enable();
1299 }
1300
1301 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1302
1303 if (error_code & X86_PF_WRITE)
1304 flags |= FAULT_FLAG_WRITE;
1305 if (error_code & X86_PF_INSTR)
1306 flags |= FAULT_FLAG_INSTRUCTION;
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 /*
1327 * Kernel-mode access to the user address space should only occur
1328 * on well-defined single instructions listed in the exception
1329 * tables. But, an erroneous kernel fault occurring outside one of
1330 * those areas which also holds mmap_lock might deadlock attempting
1331 * to validate the fault against the address space.
1332 *
1333 * Only do the expensive exception table search when we might be at
1334 * risk of a deadlock. This happens if we
1335 * 1. Failed to acquire mmap_lock, and
1336 * 2. The access did not originate in userspace.
1337 */
1338 if (unlikely(!mmap_read_trylock(mm))) {
1339 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1340 /*
1341 * Fault from code in kernel from
1342 * which we do not expect faults.
1343 */
1344 bad_area_nosemaphore(regs, error_code, address);
1345 return;
1346 }
1347retry:
1348 mmap_read_lock(mm);
1349 } else {
1350 /*
1351 * The above down_read_trylock() might have succeeded in
1352 * which case we'll have missed the might_sleep() from
1353 * down_read():
1354 */
1355 might_sleep();
1356 }
1357
1358 vma = find_vma(mm, address);
1359 if (unlikely(!vma)) {
1360 bad_area(regs, error_code, address);
1361 return;
1362 }
1363 if (likely(vma->vm_start <= address))
1364 goto good_area;
1365 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1366 bad_area(regs, error_code, address);
1367 return;
1368 }
1369 if (unlikely(expand_stack(vma, address))) {
1370 bad_area(regs, error_code, address);
1371 return;
1372 }
1373
1374 /*
1375 * Ok, we have a good vm_area for this memory access, so
1376 * we can handle it..
1377 */
1378good_area:
1379 if (unlikely(access_error(error_code, vma))) {
1380 bad_area_access_error(regs, error_code, address, vma);
1381 return;
1382 }
1383
1384 /*
1385 * If for any reason at all we couldn't handle the fault,
1386 * make sure we exit gracefully rather than endlessly redo
1387 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1388 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1389 *
1390 * Note that handle_userfault() may also release and reacquire mmap_lock
1391 * (and not return with VM_FAULT_RETRY), when returning to userland to
1392 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1393 * (potentially after handling any pending signal during the return to
1394 * userland). The return to userland is identified whenever
1395 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1396 */
1397 fault = handle_mm_fault(vma, address, flags, regs);
1398
1399 if (fault_signal_pending(fault, regs)) {
1400 /*
1401 * Quick path to respond to signals. The core mm code
1402 * has unlocked the mm for us if we get here.
1403 */
1404 if (!user_mode(regs))
1405 kernelmode_fixup_or_oops(regs, error_code, address,
1406 SIGBUS, BUS_ADRERR,
1407 ARCH_DEFAULT_PKEY);
1408 return;
1409 }
1410
1411 /*
1412 * If we need to retry the mmap_lock has already been released,
1413 * and if there is a fatal signal pending there is no guarantee
1414 * that we made any progress. Handle this case first.
1415 */
1416 if (unlikely((fault & VM_FAULT_RETRY) &&
1417 (flags & FAULT_FLAG_ALLOW_RETRY))) {
1418 flags |= FAULT_FLAG_TRIED;
1419 goto retry;
1420 }
1421
1422 mmap_read_unlock(mm);
1423 if (likely(!(fault & VM_FAULT_ERROR)))
1424 return;
1425
1426 if (fatal_signal_pending(current) && !user_mode(regs)) {
1427 kernelmode_fixup_or_oops(regs, error_code, address,
1428 0, 0, ARCH_DEFAULT_PKEY);
1429 return;
1430 }
1431
1432 if (fault & VM_FAULT_OOM) {
1433 /* Kernel mode? Handle exceptions or die: */
1434 if (!user_mode(regs)) {
1435 kernelmode_fixup_or_oops(regs, error_code, address,
1436 SIGSEGV, SEGV_MAPERR,
1437 ARCH_DEFAULT_PKEY);
1438 return;
1439 }
1440
1441 /*
1442 * We ran out of memory, call the OOM killer, and return the
1443 * userspace (which will retry the fault, or kill us if we got
1444 * oom-killed):
1445 */
1446 pagefault_out_of_memory();
1447 } else {
1448 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1449 VM_FAULT_HWPOISON_LARGE))
1450 do_sigbus(regs, error_code, address, fault);
1451 else if (fault & VM_FAULT_SIGSEGV)
1452 bad_area_nosemaphore(regs, error_code, address);
1453 else
1454 BUG();
1455 }
1456}
1457NOKPROBE_SYMBOL(do_user_addr_fault);
1458
1459static __always_inline void
1460trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1461 unsigned long address)
1462{
1463 if (!trace_pagefault_enabled())
1464 return;
1465
1466 if (user_mode(regs))
1467 trace_page_fault_user(address, regs, error_code);
1468 else
1469 trace_page_fault_kernel(address, regs, error_code);
1470}
1471
1472static __always_inline void
1473handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1474 unsigned long address)
1475{
1476 trace_page_fault_entries(regs, error_code, address);
1477
1478 if (unlikely(kmmio_fault(regs, address)))
1479 return;
1480
1481 /* Was the fault on kernel-controlled part of the address space? */
1482 if (unlikely(fault_in_kernel_space(address))) {
1483 do_kern_addr_fault(regs, error_code, address);
1484 } else {
1485 do_user_addr_fault(regs, error_code, address);
1486 /*
1487 * User address page fault handling might have reenabled
1488 * interrupts. Fixing up all potential exit points of
1489 * do_user_addr_fault() and its leaf functions is just not
1490 * doable w/o creating an unholy mess or turning the code
1491 * upside down.
1492 */
1493 local_irq_disable();
1494 }
1495}
1496
1497DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1498{
1499 unsigned long address = read_cr2();
1500 irqentry_state_t state;
1501
1502 prefetchw(¤t->mm->mmap_lock);
1503
1504 /*
1505 * KVM uses #PF vector to deliver 'page not present' events to guests
1506 * (asynchronous page fault mechanism). The event happens when a
1507 * userspace task is trying to access some valid (from guest's point of
1508 * view) memory which is not currently mapped by the host (e.g. the
1509 * memory is swapped out). Note, the corresponding "page ready" event
1510 * which is injected when the memory becomes available, is delivered via
1511 * an interrupt mechanism and not a #PF exception
1512 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1513 *
1514 * We are relying on the interrupted context being sane (valid RSP,
1515 * relevant locks not held, etc.), which is fine as long as the
1516 * interrupted context had IF=1. We are also relying on the KVM
1517 * async pf type field and CR2 being read consistently instead of
1518 * getting values from real and async page faults mixed up.
1519 *
1520 * Fingers crossed.
1521 *
1522 * The async #PF handling code takes care of idtentry handling
1523 * itself.
1524 */
1525 if (kvm_handle_async_pf(regs, (u32)address))
1526 return;
1527
1528 /*
1529 * Entry handling for valid #PF from kernel mode is slightly
1530 * different: RCU is already watching and rcu_irq_enter() must not
1531 * be invoked because a kernel fault on a user space address might
1532 * sleep.
1533 *
1534 * In case the fault hit a RCU idle region the conditional entry
1535 * code reenabled RCU to avoid subsequent wreckage which helps
1536 * debuggability.
1537 */
1538 state = irqentry_enter(regs);
1539
1540 instrumentation_begin();
1541 handle_page_fault(regs, error_code, address);
1542 instrumentation_end();
1543
1544 irqentry_exit(regs, state);
1545}