Loading...
1/*
2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
5 */
6#include <linux/magic.h> /* STACK_END_MAGIC */
7#include <linux/sched.h> /* test_thread_flag(), ... */
8#include <linux/kdebug.h> /* oops_begin/end, ... */
9#include <linux/module.h> /* search_exception_table */
10#include <linux/bootmem.h> /* max_low_pfn */
11#include <linux/kprobes.h> /* __kprobes, ... */
12#include <linux/mmiotrace.h> /* kmmio_handler, ... */
13#include <linux/perf_event.h> /* perf_sw_event */
14#include <linux/hugetlb.h> /* hstate_index_to_shift */
15#include <linux/prefetch.h> /* prefetchw */
16#include <linux/context_tracking.h> /* exception_enter(), ... */
17
18#include <asm/traps.h> /* dotraplinkage, ... */
19#include <asm/pgalloc.h> /* pgd_*(), ... */
20#include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
21#include <asm/fixmap.h> /* VSYSCALL_START */
22
23#define CREATE_TRACE_POINTS
24#include <asm/trace/exceptions.h>
25
26/*
27 * Page fault error code bits:
28 *
29 * bit 0 == 0: no page found 1: protection fault
30 * bit 1 == 0: read access 1: write access
31 * bit 2 == 0: kernel-mode access 1: user-mode access
32 * bit 3 == 1: use of reserved bit detected
33 * bit 4 == 1: fault was an instruction fetch
34 */
35enum x86_pf_error_code {
36
37 PF_PROT = 1 << 0,
38 PF_WRITE = 1 << 1,
39 PF_USER = 1 << 2,
40 PF_RSVD = 1 << 3,
41 PF_INSTR = 1 << 4,
42};
43
44/*
45 * Returns 0 if mmiotrace is disabled, or if the fault is not
46 * handled by mmiotrace:
47 */
48static inline int __kprobes
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
57static inline int __kprobes kprobes_fault(struct pt_regs *regs)
58{
59 int ret = 0;
60
61 /* kprobe_running() needs smp_processor_id() */
62 if (kprobes_built_in() && !user_mode_vm(regs)) {
63 preempt_disable();
64 if (kprobe_running() && kprobe_fault_handler(regs, 14))
65 ret = 1;
66 preempt_enable();
67 }
68
69 return ret;
70}
71
72/*
73 * Prefetch quirks:
74 *
75 * 32-bit mode:
76 *
77 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
78 * Check that here and ignore it.
79 *
80 * 64-bit mode:
81 *
82 * Sometimes the CPU reports invalid exceptions on prefetch.
83 * Check that here and ignore it.
84 *
85 * Opcode checker based on code by Richard Brunner.
86 */
87static inline int
88check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
89 unsigned char opcode, int *prefetch)
90{
91 unsigned char instr_hi = opcode & 0xf0;
92 unsigned char instr_lo = opcode & 0x0f;
93
94 switch (instr_hi) {
95 case 0x20:
96 case 0x30:
97 /*
98 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
99 * In X86_64 long mode, the CPU will signal invalid
100 * opcode if some of these prefixes are present so
101 * X86_64 will never get here anyway
102 */
103 return ((instr_lo & 7) == 0x6);
104#ifdef CONFIG_X86_64
105 case 0x40:
106 /*
107 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
108 * Need to figure out under what instruction mode the
109 * instruction was issued. Could check the LDT for lm,
110 * but for now it's good enough to assume that long
111 * mode only uses well known segments or kernel.
112 */
113 return (!user_mode(regs) || user_64bit_mode(regs));
114#endif
115 case 0x60:
116 /* 0x64 thru 0x67 are valid prefixes in all modes. */
117 return (instr_lo & 0xC) == 0x4;
118 case 0xF0:
119 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
120 return !instr_lo || (instr_lo>>1) == 1;
121 case 0x00:
122 /* Prefetch instruction is 0x0F0D or 0x0F18 */
123 if (probe_kernel_address(instr, opcode))
124 return 0;
125
126 *prefetch = (instr_lo == 0xF) &&
127 (opcode == 0x0D || opcode == 0x18);
128 return 0;
129 default:
130 return 0;
131 }
132}
133
134static int
135is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
136{
137 unsigned char *max_instr;
138 unsigned char *instr;
139 int prefetch = 0;
140
141 /*
142 * If it was a exec (instruction fetch) fault on NX page, then
143 * do not ignore the fault:
144 */
145 if (error_code & PF_INSTR)
146 return 0;
147
148 instr = (void *)convert_ip_to_linear(current, regs);
149 max_instr = instr + 15;
150
151 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
152 return 0;
153
154 while (instr < max_instr) {
155 unsigned char opcode;
156
157 if (probe_kernel_address(instr, opcode))
158 break;
159
160 instr++;
161
162 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
163 break;
164 }
165 return prefetch;
166}
167
168static void
169force_sig_info_fault(int si_signo, int si_code, unsigned long address,
170 struct task_struct *tsk, int fault)
171{
172 unsigned lsb = 0;
173 siginfo_t info;
174
175 info.si_signo = si_signo;
176 info.si_errno = 0;
177 info.si_code = si_code;
178 info.si_addr = (void __user *)address;
179 if (fault & VM_FAULT_HWPOISON_LARGE)
180 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
181 if (fault & VM_FAULT_HWPOISON)
182 lsb = PAGE_SHIFT;
183 info.si_addr_lsb = lsb;
184
185 force_sig_info(si_signo, &info, tsk);
186}
187
188DEFINE_SPINLOCK(pgd_lock);
189LIST_HEAD(pgd_list);
190
191#ifdef CONFIG_X86_32
192static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
193{
194 unsigned index = pgd_index(address);
195 pgd_t *pgd_k;
196 pud_t *pud, *pud_k;
197 pmd_t *pmd, *pmd_k;
198
199 pgd += index;
200 pgd_k = init_mm.pgd + index;
201
202 if (!pgd_present(*pgd_k))
203 return NULL;
204
205 /*
206 * set_pgd(pgd, *pgd_k); here would be useless on PAE
207 * and redundant with the set_pmd() on non-PAE. As would
208 * set_pud.
209 */
210 pud = pud_offset(pgd, address);
211 pud_k = pud_offset(pgd_k, address);
212 if (!pud_present(*pud_k))
213 return NULL;
214
215 pmd = pmd_offset(pud, address);
216 pmd_k = pmd_offset(pud_k, address);
217 if (!pmd_present(*pmd_k))
218 return NULL;
219
220 if (!pmd_present(*pmd))
221 set_pmd(pmd, *pmd_k);
222 else
223 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
224
225 return pmd_k;
226}
227
228void vmalloc_sync_all(void)
229{
230 unsigned long address;
231
232 if (SHARED_KERNEL_PMD)
233 return;
234
235 for (address = VMALLOC_START & PMD_MASK;
236 address >= TASK_SIZE && address < FIXADDR_TOP;
237 address += PMD_SIZE) {
238 struct page *page;
239
240 spin_lock(&pgd_lock);
241 list_for_each_entry(page, &pgd_list, lru) {
242 spinlock_t *pgt_lock;
243 pmd_t *ret;
244
245 /* the pgt_lock only for Xen */
246 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
247
248 spin_lock(pgt_lock);
249 ret = vmalloc_sync_one(page_address(page), address);
250 spin_unlock(pgt_lock);
251
252 if (!ret)
253 break;
254 }
255 spin_unlock(&pgd_lock);
256 }
257}
258
259/*
260 * 32-bit:
261 *
262 * Handle a fault on the vmalloc or module mapping area
263 */
264static noinline __kprobes int vmalloc_fault(unsigned long address)
265{
266 unsigned long pgd_paddr;
267 pmd_t *pmd_k;
268 pte_t *pte_k;
269
270 /* Make sure we are in vmalloc area: */
271 if (!(address >= VMALLOC_START && address < VMALLOC_END))
272 return -1;
273
274 WARN_ON_ONCE(in_nmi());
275
276 /*
277 * Synchronize this task's top level page-table
278 * with the 'reference' page table.
279 *
280 * Do _not_ use "current" here. We might be inside
281 * an interrupt in the middle of a task switch..
282 */
283 pgd_paddr = read_cr3();
284 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
285 if (!pmd_k)
286 return -1;
287
288 pte_k = pte_offset_kernel(pmd_k, address);
289 if (!pte_present(*pte_k))
290 return -1;
291
292 return 0;
293}
294
295/*
296 * Did it hit the DOS screen memory VA from vm86 mode?
297 */
298static inline void
299check_v8086_mode(struct pt_regs *regs, unsigned long address,
300 struct task_struct *tsk)
301{
302 unsigned long bit;
303
304 if (!v8086_mode(regs))
305 return;
306
307 bit = (address - 0xA0000) >> PAGE_SHIFT;
308 if (bit < 32)
309 tsk->thread.screen_bitmap |= 1 << bit;
310}
311
312static bool low_pfn(unsigned long pfn)
313{
314 return pfn < max_low_pfn;
315}
316
317static void dump_pagetable(unsigned long address)
318{
319 pgd_t *base = __va(read_cr3());
320 pgd_t *pgd = &base[pgd_index(address)];
321 pmd_t *pmd;
322 pte_t *pte;
323
324#ifdef CONFIG_X86_PAE
325 printk("*pdpt = %016Lx ", pgd_val(*pgd));
326 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
327 goto out;
328#endif
329 pmd = pmd_offset(pud_offset(pgd, address), address);
330 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
331
332 /*
333 * We must not directly access the pte in the highpte
334 * case if the page table is located in highmem.
335 * And let's rather not kmap-atomic the pte, just in case
336 * it's allocated already:
337 */
338 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
339 goto out;
340
341 pte = pte_offset_kernel(pmd, address);
342 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
343out:
344 printk("\n");
345}
346
347#else /* CONFIG_X86_64: */
348
349void vmalloc_sync_all(void)
350{
351 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
352}
353
354/*
355 * 64-bit:
356 *
357 * Handle a fault on the vmalloc area
358 *
359 * This assumes no large pages in there.
360 */
361static noinline __kprobes int vmalloc_fault(unsigned long address)
362{
363 pgd_t *pgd, *pgd_ref;
364 pud_t *pud, *pud_ref;
365 pmd_t *pmd, *pmd_ref;
366 pte_t *pte, *pte_ref;
367
368 /* Make sure we are in vmalloc area: */
369 if (!(address >= VMALLOC_START && address < VMALLOC_END))
370 return -1;
371
372 WARN_ON_ONCE(in_nmi());
373
374 /*
375 * Copy kernel mappings over when needed. This can also
376 * happen within a race in page table update. In the later
377 * case just flush:
378 */
379 pgd = pgd_offset(current->active_mm, address);
380 pgd_ref = pgd_offset_k(address);
381 if (pgd_none(*pgd_ref))
382 return -1;
383
384 if (pgd_none(*pgd)) {
385 set_pgd(pgd, *pgd_ref);
386 arch_flush_lazy_mmu_mode();
387 } else {
388 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
389 }
390
391 /*
392 * Below here mismatches are bugs because these lower tables
393 * are shared:
394 */
395
396 pud = pud_offset(pgd, address);
397 pud_ref = pud_offset(pgd_ref, address);
398 if (pud_none(*pud_ref))
399 return -1;
400
401 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
402 BUG();
403
404 pmd = pmd_offset(pud, address);
405 pmd_ref = pmd_offset(pud_ref, address);
406 if (pmd_none(*pmd_ref))
407 return -1;
408
409 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
410 BUG();
411
412 pte_ref = pte_offset_kernel(pmd_ref, address);
413 if (!pte_present(*pte_ref))
414 return -1;
415
416 pte = pte_offset_kernel(pmd, address);
417
418 /*
419 * Don't use pte_page here, because the mappings can point
420 * outside mem_map, and the NUMA hash lookup cannot handle
421 * that:
422 */
423 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
424 BUG();
425
426 return 0;
427}
428
429#ifdef CONFIG_CPU_SUP_AMD
430static const char errata93_warning[] =
431KERN_ERR
432"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
433"******* Working around it, but it may cause SEGVs or burn power.\n"
434"******* Please consider a BIOS update.\n"
435"******* Disabling USB legacy in the BIOS may also help.\n";
436#endif
437
438/*
439 * No vm86 mode in 64-bit mode:
440 */
441static inline void
442check_v8086_mode(struct pt_regs *regs, unsigned long address,
443 struct task_struct *tsk)
444{
445}
446
447static int bad_address(void *p)
448{
449 unsigned long dummy;
450
451 return probe_kernel_address((unsigned long *)p, dummy);
452}
453
454static void dump_pagetable(unsigned long address)
455{
456 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
457 pgd_t *pgd = base + pgd_index(address);
458 pud_t *pud;
459 pmd_t *pmd;
460 pte_t *pte;
461
462 if (bad_address(pgd))
463 goto bad;
464
465 printk("PGD %lx ", pgd_val(*pgd));
466
467 if (!pgd_present(*pgd))
468 goto out;
469
470 pud = pud_offset(pgd, address);
471 if (bad_address(pud))
472 goto bad;
473
474 printk("PUD %lx ", pud_val(*pud));
475 if (!pud_present(*pud) || pud_large(*pud))
476 goto out;
477
478 pmd = pmd_offset(pud, address);
479 if (bad_address(pmd))
480 goto bad;
481
482 printk("PMD %lx ", pmd_val(*pmd));
483 if (!pmd_present(*pmd) || pmd_large(*pmd))
484 goto out;
485
486 pte = pte_offset_kernel(pmd, address);
487 if (bad_address(pte))
488 goto bad;
489
490 printk("PTE %lx", pte_val(*pte));
491out:
492 printk("\n");
493 return;
494bad:
495 printk("BAD\n");
496}
497
498#endif /* CONFIG_X86_64 */
499
500/*
501 * Workaround for K8 erratum #93 & buggy BIOS.
502 *
503 * BIOS SMM functions are required to use a specific workaround
504 * to avoid corruption of the 64bit RIP register on C stepping K8.
505 *
506 * A lot of BIOS that didn't get tested properly miss this.
507 *
508 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
509 * Try to work around it here.
510 *
511 * Note we only handle faults in kernel here.
512 * Does nothing on 32-bit.
513 */
514static int is_errata93(struct pt_regs *regs, unsigned long address)
515{
516#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
517 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
518 || boot_cpu_data.x86 != 0xf)
519 return 0;
520
521 if (address != regs->ip)
522 return 0;
523
524 if ((address >> 32) != 0)
525 return 0;
526
527 address |= 0xffffffffUL << 32;
528 if ((address >= (u64)_stext && address <= (u64)_etext) ||
529 (address >= MODULES_VADDR && address <= MODULES_END)) {
530 printk_once(errata93_warning);
531 regs->ip = address;
532 return 1;
533 }
534#endif
535 return 0;
536}
537
538/*
539 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
540 * to illegal addresses >4GB.
541 *
542 * We catch this in the page fault handler because these addresses
543 * are not reachable. Just detect this case and return. Any code
544 * segment in LDT is compatibility mode.
545 */
546static int is_errata100(struct pt_regs *regs, unsigned long address)
547{
548#ifdef CONFIG_X86_64
549 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
550 return 1;
551#endif
552 return 0;
553}
554
555static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
556{
557#ifdef CONFIG_X86_F00F_BUG
558 unsigned long nr;
559
560 /*
561 * Pentium F0 0F C7 C8 bug workaround:
562 */
563 if (boot_cpu_has_bug(X86_BUG_F00F)) {
564 nr = (address - idt_descr.address) >> 3;
565
566 if (nr == 6) {
567 do_invalid_op(regs, 0);
568 return 1;
569 }
570 }
571#endif
572 return 0;
573}
574
575static const char nx_warning[] = KERN_CRIT
576"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
577
578static void
579show_fault_oops(struct pt_regs *regs, unsigned long error_code,
580 unsigned long address)
581{
582 if (!oops_may_print())
583 return;
584
585 if (error_code & PF_INSTR) {
586 unsigned int level;
587 pgd_t *pgd;
588 pte_t *pte;
589
590 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
591 pgd += pgd_index(address);
592
593 pte = lookup_address_in_pgd(pgd, address, &level);
594
595 if (pte && pte_present(*pte) && !pte_exec(*pte))
596 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
597 }
598
599 printk(KERN_ALERT "BUG: unable to handle kernel ");
600 if (address < PAGE_SIZE)
601 printk(KERN_CONT "NULL pointer dereference");
602 else
603 printk(KERN_CONT "paging request");
604
605 printk(KERN_CONT " at %p\n", (void *) address);
606 printk(KERN_ALERT "IP:");
607 printk_address(regs->ip);
608
609 dump_pagetable(address);
610}
611
612static noinline void
613pgtable_bad(struct pt_regs *regs, unsigned long error_code,
614 unsigned long address)
615{
616 struct task_struct *tsk;
617 unsigned long flags;
618 int sig;
619
620 flags = oops_begin();
621 tsk = current;
622 sig = SIGKILL;
623
624 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
625 tsk->comm, address);
626 dump_pagetable(address);
627
628 tsk->thread.cr2 = address;
629 tsk->thread.trap_nr = X86_TRAP_PF;
630 tsk->thread.error_code = error_code;
631
632 if (__die("Bad pagetable", regs, error_code))
633 sig = 0;
634
635 oops_end(flags, regs, sig);
636}
637
638static noinline void
639no_context(struct pt_regs *regs, unsigned long error_code,
640 unsigned long address, int signal, int si_code)
641{
642 struct task_struct *tsk = current;
643 unsigned long *stackend;
644 unsigned long flags;
645 int sig;
646
647 /* Are we prepared to handle this kernel fault? */
648 if (fixup_exception(regs)) {
649 /*
650 * Any interrupt that takes a fault gets the fixup. This makes
651 * the below recursive fault logic only apply to a faults from
652 * task context.
653 */
654 if (in_interrupt())
655 return;
656
657 /*
658 * Per the above we're !in_interrupt(), aka. task context.
659 *
660 * In this case we need to make sure we're not recursively
661 * faulting through the emulate_vsyscall() logic.
662 */
663 if (current_thread_info()->sig_on_uaccess_error && signal) {
664 tsk->thread.trap_nr = X86_TRAP_PF;
665 tsk->thread.error_code = error_code | PF_USER;
666 tsk->thread.cr2 = address;
667
668 /* XXX: hwpoison faults will set the wrong code. */
669 force_sig_info_fault(signal, si_code, address, tsk, 0);
670 }
671
672 /*
673 * Barring that, we can do the fixup and be happy.
674 */
675 return;
676 }
677
678 /*
679 * 32-bit:
680 *
681 * Valid to do another page fault here, because if this fault
682 * had been triggered by is_prefetch fixup_exception would have
683 * handled it.
684 *
685 * 64-bit:
686 *
687 * Hall of shame of CPU/BIOS bugs.
688 */
689 if (is_prefetch(regs, error_code, address))
690 return;
691
692 if (is_errata93(regs, address))
693 return;
694
695 /*
696 * Oops. The kernel tried to access some bad page. We'll have to
697 * terminate things with extreme prejudice:
698 */
699 flags = oops_begin();
700
701 show_fault_oops(regs, error_code, address);
702
703 stackend = end_of_stack(tsk);
704 if (tsk != &init_task && *stackend != STACK_END_MAGIC)
705 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
706
707 tsk->thread.cr2 = address;
708 tsk->thread.trap_nr = X86_TRAP_PF;
709 tsk->thread.error_code = error_code;
710
711 sig = SIGKILL;
712 if (__die("Oops", regs, error_code))
713 sig = 0;
714
715 /* Executive summary in case the body of the oops scrolled away */
716 printk(KERN_DEFAULT "CR2: %016lx\n", address);
717
718 oops_end(flags, regs, sig);
719}
720
721/*
722 * Print out info about fatal segfaults, if the show_unhandled_signals
723 * sysctl is set:
724 */
725static inline void
726show_signal_msg(struct pt_regs *regs, unsigned long error_code,
727 unsigned long address, struct task_struct *tsk)
728{
729 if (!unhandled_signal(tsk, SIGSEGV))
730 return;
731
732 if (!printk_ratelimit())
733 return;
734
735 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
736 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
737 tsk->comm, task_pid_nr(tsk), address,
738 (void *)regs->ip, (void *)regs->sp, error_code);
739
740 print_vma_addr(KERN_CONT " in ", regs->ip);
741
742 printk(KERN_CONT "\n");
743}
744
745static void
746__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
747 unsigned long address, int si_code)
748{
749 struct task_struct *tsk = current;
750
751 /* User mode accesses just cause a SIGSEGV */
752 if (error_code & PF_USER) {
753 /*
754 * It's possible to have interrupts off here:
755 */
756 local_irq_enable();
757
758 /*
759 * Valid to do another page fault here because this one came
760 * from user space:
761 */
762 if (is_prefetch(regs, error_code, address))
763 return;
764
765 if (is_errata100(regs, address))
766 return;
767
768#ifdef CONFIG_X86_64
769 /*
770 * Instruction fetch faults in the vsyscall page might need
771 * emulation.
772 */
773 if (unlikely((error_code & PF_INSTR) &&
774 ((address & ~0xfff) == VSYSCALL_START))) {
775 if (emulate_vsyscall(regs, address))
776 return;
777 }
778#endif
779 /* Kernel addresses are always protection faults: */
780 if (address >= TASK_SIZE)
781 error_code |= PF_PROT;
782
783 if (likely(show_unhandled_signals))
784 show_signal_msg(regs, error_code, address, tsk);
785
786 tsk->thread.cr2 = address;
787 tsk->thread.error_code = error_code;
788 tsk->thread.trap_nr = X86_TRAP_PF;
789
790 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
791
792 return;
793 }
794
795 if (is_f00f_bug(regs, address))
796 return;
797
798 no_context(regs, error_code, address, SIGSEGV, si_code);
799}
800
801static noinline void
802bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
803 unsigned long address)
804{
805 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
806}
807
808static void
809__bad_area(struct pt_regs *regs, unsigned long error_code,
810 unsigned long address, int si_code)
811{
812 struct mm_struct *mm = current->mm;
813
814 /*
815 * Something tried to access memory that isn't in our memory map..
816 * Fix it, but check if it's kernel or user first..
817 */
818 up_read(&mm->mmap_sem);
819
820 __bad_area_nosemaphore(regs, error_code, address, si_code);
821}
822
823static noinline void
824bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
825{
826 __bad_area(regs, error_code, address, SEGV_MAPERR);
827}
828
829static noinline void
830bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
831 unsigned long address)
832{
833 __bad_area(regs, error_code, address, SEGV_ACCERR);
834}
835
836static void
837do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
838 unsigned int fault)
839{
840 struct task_struct *tsk = current;
841 struct mm_struct *mm = tsk->mm;
842 int code = BUS_ADRERR;
843
844 up_read(&mm->mmap_sem);
845
846 /* Kernel mode? Handle exceptions or die: */
847 if (!(error_code & PF_USER)) {
848 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
849 return;
850 }
851
852 /* User-space => ok to do another page fault: */
853 if (is_prefetch(regs, error_code, address))
854 return;
855
856 tsk->thread.cr2 = address;
857 tsk->thread.error_code = error_code;
858 tsk->thread.trap_nr = X86_TRAP_PF;
859
860#ifdef CONFIG_MEMORY_FAILURE
861 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
862 printk(KERN_ERR
863 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
864 tsk->comm, tsk->pid, address);
865 code = BUS_MCEERR_AR;
866 }
867#endif
868 force_sig_info_fault(SIGBUS, code, address, tsk, fault);
869}
870
871static noinline void
872mm_fault_error(struct pt_regs *regs, unsigned long error_code,
873 unsigned long address, unsigned int fault)
874{
875 if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
876 up_read(¤t->mm->mmap_sem);
877 no_context(regs, error_code, address, 0, 0);
878 return;
879 }
880
881 if (fault & VM_FAULT_OOM) {
882 /* Kernel mode? Handle exceptions or die: */
883 if (!(error_code & PF_USER)) {
884 up_read(¤t->mm->mmap_sem);
885 no_context(regs, error_code, address,
886 SIGSEGV, SEGV_MAPERR);
887 return;
888 }
889
890 up_read(¤t->mm->mmap_sem);
891
892 /*
893 * We ran out of memory, call the OOM killer, and return the
894 * userspace (which will retry the fault, or kill us if we got
895 * oom-killed):
896 */
897 pagefault_out_of_memory();
898 } else {
899 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
900 VM_FAULT_HWPOISON_LARGE))
901 do_sigbus(regs, error_code, address, fault);
902 else
903 BUG();
904 }
905}
906
907static int spurious_fault_check(unsigned long error_code, pte_t *pte)
908{
909 if ((error_code & PF_WRITE) && !pte_write(*pte))
910 return 0;
911
912 if ((error_code & PF_INSTR) && !pte_exec(*pte))
913 return 0;
914
915 return 1;
916}
917
918/*
919 * Handle a spurious fault caused by a stale TLB entry.
920 *
921 * This allows us to lazily refresh the TLB when increasing the
922 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
923 * eagerly is very expensive since that implies doing a full
924 * cross-processor TLB flush, even if no stale TLB entries exist
925 * on other processors.
926 *
927 * There are no security implications to leaving a stale TLB when
928 * increasing the permissions on a page.
929 */
930static noinline __kprobes int
931spurious_fault(unsigned long error_code, unsigned long address)
932{
933 pgd_t *pgd;
934 pud_t *pud;
935 pmd_t *pmd;
936 pte_t *pte;
937 int ret;
938
939 /* Reserved-bit violation or user access to kernel space? */
940 if (error_code & (PF_USER | PF_RSVD))
941 return 0;
942
943 pgd = init_mm.pgd + pgd_index(address);
944 if (!pgd_present(*pgd))
945 return 0;
946
947 pud = pud_offset(pgd, address);
948 if (!pud_present(*pud))
949 return 0;
950
951 if (pud_large(*pud))
952 return spurious_fault_check(error_code, (pte_t *) pud);
953
954 pmd = pmd_offset(pud, address);
955 if (!pmd_present(*pmd))
956 return 0;
957
958 if (pmd_large(*pmd))
959 return spurious_fault_check(error_code, (pte_t *) pmd);
960
961 pte = pte_offset_kernel(pmd, address);
962 if (!pte_present(*pte))
963 return 0;
964
965 ret = spurious_fault_check(error_code, pte);
966 if (!ret)
967 return 0;
968
969 /*
970 * Make sure we have permissions in PMD.
971 * If not, then there's a bug in the page tables:
972 */
973 ret = spurious_fault_check(error_code, (pte_t *) pmd);
974 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
975
976 return ret;
977}
978
979int show_unhandled_signals = 1;
980
981static inline int
982access_error(unsigned long error_code, struct vm_area_struct *vma)
983{
984 if (error_code & PF_WRITE) {
985 /* write, present and write, not present: */
986 if (unlikely(!(vma->vm_flags & VM_WRITE)))
987 return 1;
988 return 0;
989 }
990
991 /* read, present: */
992 if (unlikely(error_code & PF_PROT))
993 return 1;
994
995 /* read, not present: */
996 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
997 return 1;
998
999 return 0;
1000}
1001
1002static int fault_in_kernel_space(unsigned long address)
1003{
1004 return address >= TASK_SIZE_MAX;
1005}
1006
1007static inline bool smap_violation(int error_code, struct pt_regs *regs)
1008{
1009 if (!IS_ENABLED(CONFIG_X86_SMAP))
1010 return false;
1011
1012 if (!static_cpu_has(X86_FEATURE_SMAP))
1013 return false;
1014
1015 if (error_code & PF_USER)
1016 return false;
1017
1018 if (!user_mode_vm(regs) && (regs->flags & X86_EFLAGS_AC))
1019 return false;
1020
1021 return true;
1022}
1023
1024/*
1025 * This routine handles page faults. It determines the address,
1026 * and the problem, and then passes it off to one of the appropriate
1027 * routines.
1028 *
1029 * This function must have noinline because both callers
1030 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1031 * guarantees there's a function trace entry.
1032 */
1033static void __kprobes noinline
1034__do_page_fault(struct pt_regs *regs, unsigned long error_code,
1035 unsigned long address)
1036{
1037 struct vm_area_struct *vma;
1038 struct task_struct *tsk;
1039 struct mm_struct *mm;
1040 int fault;
1041 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1042
1043 tsk = current;
1044 mm = tsk->mm;
1045
1046 /*
1047 * Detect and handle instructions that would cause a page fault for
1048 * both a tracked kernel page and a userspace page.
1049 */
1050 if (kmemcheck_active(regs))
1051 kmemcheck_hide(regs);
1052 prefetchw(&mm->mmap_sem);
1053
1054 if (unlikely(kmmio_fault(regs, address)))
1055 return;
1056
1057 /*
1058 * We fault-in kernel-space virtual memory on-demand. The
1059 * 'reference' page table is init_mm.pgd.
1060 *
1061 * NOTE! We MUST NOT take any locks for this case. We may
1062 * be in an interrupt or a critical region, and should
1063 * only copy the information from the master page table,
1064 * nothing more.
1065 *
1066 * This verifies that the fault happens in kernel space
1067 * (error_code & 4) == 0, and that the fault was not a
1068 * protection error (error_code & 9) == 0.
1069 */
1070 if (unlikely(fault_in_kernel_space(address))) {
1071 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1072 if (vmalloc_fault(address) >= 0)
1073 return;
1074
1075 if (kmemcheck_fault(regs, address, error_code))
1076 return;
1077 }
1078
1079 /* Can handle a stale RO->RW TLB: */
1080 if (spurious_fault(error_code, address))
1081 return;
1082
1083 /* kprobes don't want to hook the spurious faults: */
1084 if (kprobes_fault(regs))
1085 return;
1086 /*
1087 * Don't take the mm semaphore here. If we fixup a prefetch
1088 * fault we could otherwise deadlock:
1089 */
1090 bad_area_nosemaphore(regs, error_code, address);
1091
1092 return;
1093 }
1094
1095 /* kprobes don't want to hook the spurious faults: */
1096 if (unlikely(kprobes_fault(regs)))
1097 return;
1098
1099 if (unlikely(error_code & PF_RSVD))
1100 pgtable_bad(regs, error_code, address);
1101
1102 if (unlikely(smap_violation(error_code, regs))) {
1103 bad_area_nosemaphore(regs, error_code, address);
1104 return;
1105 }
1106
1107 /*
1108 * If we're in an interrupt, have no user context or are running
1109 * in an atomic region then we must not take the fault:
1110 */
1111 if (unlikely(in_atomic() || !mm)) {
1112 bad_area_nosemaphore(regs, error_code, address);
1113 return;
1114 }
1115
1116 /*
1117 * It's safe to allow irq's after cr2 has been saved and the
1118 * vmalloc fault has been handled.
1119 *
1120 * User-mode registers count as a user access even for any
1121 * potential system fault or CPU buglet:
1122 */
1123 if (user_mode_vm(regs)) {
1124 local_irq_enable();
1125 error_code |= PF_USER;
1126 flags |= FAULT_FLAG_USER;
1127 } else {
1128 if (regs->flags & X86_EFLAGS_IF)
1129 local_irq_enable();
1130 }
1131
1132 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1133
1134 if (error_code & PF_WRITE)
1135 flags |= FAULT_FLAG_WRITE;
1136
1137 /*
1138 * When running in the kernel we expect faults to occur only to
1139 * addresses in user space. All other faults represent errors in
1140 * the kernel and should generate an OOPS. Unfortunately, in the
1141 * case of an erroneous fault occurring in a code path which already
1142 * holds mmap_sem we will deadlock attempting to validate the fault
1143 * against the address space. Luckily the kernel only validly
1144 * references user space from well defined areas of code, which are
1145 * listed in the exceptions table.
1146 *
1147 * As the vast majority of faults will be valid we will only perform
1148 * the source reference check when there is a possibility of a
1149 * deadlock. Attempt to lock the address space, if we cannot we then
1150 * validate the source. If this is invalid we can skip the address
1151 * space check, thus avoiding the deadlock:
1152 */
1153 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1154 if ((error_code & PF_USER) == 0 &&
1155 !search_exception_tables(regs->ip)) {
1156 bad_area_nosemaphore(regs, error_code, address);
1157 return;
1158 }
1159retry:
1160 down_read(&mm->mmap_sem);
1161 } else {
1162 /*
1163 * The above down_read_trylock() might have succeeded in
1164 * which case we'll have missed the might_sleep() from
1165 * down_read():
1166 */
1167 might_sleep();
1168 }
1169
1170 vma = find_vma(mm, address);
1171 if (unlikely(!vma)) {
1172 bad_area(regs, error_code, address);
1173 return;
1174 }
1175 if (likely(vma->vm_start <= address))
1176 goto good_area;
1177 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1178 bad_area(regs, error_code, address);
1179 return;
1180 }
1181 if (error_code & PF_USER) {
1182 /*
1183 * Accessing the stack below %sp is always a bug.
1184 * The large cushion allows instructions like enter
1185 * and pusha to work. ("enter $65535, $31" pushes
1186 * 32 pointers and then decrements %sp by 65535.)
1187 */
1188 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1189 bad_area(regs, error_code, address);
1190 return;
1191 }
1192 }
1193 if (unlikely(expand_stack(vma, address))) {
1194 bad_area(regs, error_code, address);
1195 return;
1196 }
1197
1198 /*
1199 * Ok, we have a good vm_area for this memory access, so
1200 * we can handle it..
1201 */
1202good_area:
1203 if (unlikely(access_error(error_code, vma))) {
1204 bad_area_access_error(regs, error_code, address);
1205 return;
1206 }
1207
1208 /*
1209 * If for any reason at all we couldn't handle the fault,
1210 * make sure we exit gracefully rather than endlessly redo
1211 * the fault:
1212 */
1213 fault = handle_mm_fault(mm, vma, address, flags);
1214
1215 /*
1216 * If we need to retry but a fatal signal is pending, handle the
1217 * signal first. We do not need to release the mmap_sem because it
1218 * would already be released in __lock_page_or_retry in mm/filemap.c.
1219 */
1220 if (unlikely((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)))
1221 return;
1222
1223 if (unlikely(fault & VM_FAULT_ERROR)) {
1224 mm_fault_error(regs, error_code, address, fault);
1225 return;
1226 }
1227
1228 /*
1229 * Major/minor page fault accounting is only done on the
1230 * initial attempt. If we go through a retry, it is extremely
1231 * likely that the page will be found in page cache at that point.
1232 */
1233 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1234 if (fault & VM_FAULT_MAJOR) {
1235 tsk->maj_flt++;
1236 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
1237 regs, address);
1238 } else {
1239 tsk->min_flt++;
1240 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
1241 regs, address);
1242 }
1243 if (fault & VM_FAULT_RETRY) {
1244 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
1245 * of starvation. */
1246 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1247 flags |= FAULT_FLAG_TRIED;
1248 goto retry;
1249 }
1250 }
1251
1252 check_v8086_mode(regs, address, tsk);
1253
1254 up_read(&mm->mmap_sem);
1255}
1256
1257dotraplinkage void __kprobes notrace
1258do_page_fault(struct pt_regs *regs, unsigned long error_code)
1259{
1260 unsigned long address = read_cr2(); /* Get the faulting address */
1261 enum ctx_state prev_state;
1262
1263 /*
1264 * We must have this function tagged with __kprobes, notrace and call
1265 * read_cr2() before calling anything else. To avoid calling any kind
1266 * of tracing machinery before we've observed the CR2 value.
1267 *
1268 * exception_{enter,exit}() contain all sorts of tracepoints.
1269 */
1270
1271 prev_state = exception_enter();
1272 __do_page_fault(regs, error_code, address);
1273 exception_exit(prev_state);
1274}
1275
1276#ifdef CONFIG_TRACING
1277static void trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1278 unsigned long error_code)
1279{
1280 if (user_mode(regs))
1281 trace_page_fault_user(address, regs, error_code);
1282 else
1283 trace_page_fault_kernel(address, regs, error_code);
1284}
1285
1286dotraplinkage void __kprobes notrace
1287trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1288{
1289 /*
1290 * The exception_enter and tracepoint processing could
1291 * trigger another page faults (user space callchain
1292 * reading) and destroy the original cr2 value, so read
1293 * the faulting address now.
1294 */
1295 unsigned long address = read_cr2();
1296 enum ctx_state prev_state;
1297
1298 prev_state = exception_enter();
1299 trace_page_fault_entries(address, regs, error_code);
1300 __do_page_fault(regs, error_code, address);
1301 exception_exit(prev_state);
1302}
1303#endif /* CONFIG_TRACING */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1995 Linus Torvalds
4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 */
7#include <linux/sched.h> /* test_thread_flag(), ... */
8#include <linux/sched/task_stack.h> /* task_stack_*(), ... */
9#include <linux/kdebug.h> /* oops_begin/end, ... */
10#include <linux/extable.h> /* search_exception_tables */
11#include <linux/memblock.h> /* max_low_pfn */
12#include <linux/kfence.h> /* kfence_handle_page_fault */
13#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
14#include <linux/mmiotrace.h> /* kmmio_handler, ... */
15#include <linux/perf_event.h> /* perf_sw_event */
16#include <linux/hugetlb.h> /* hstate_index_to_shift */
17#include <linux/prefetch.h> /* prefetchw */
18#include <linux/context_tracking.h> /* exception_enter(), ... */
19#include <linux/uaccess.h> /* faulthandler_disabled() */
20#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
21#include <linux/mm_types.h>
22#include <linux/mm.h> /* find_and_lock_vma() */
23
24#include <asm/cpufeature.h> /* boot_cpu_has, ... */
25#include <asm/traps.h> /* dotraplinkage, ... */
26#include <asm/fixmap.h> /* VSYSCALL_ADDR */
27#include <asm/vsyscall.h> /* emulate_vsyscall */
28#include <asm/vm86.h> /* struct vm86 */
29#include <asm/mmu_context.h> /* vma_pkey() */
30#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
31#include <asm/desc.h> /* store_idt(), ... */
32#include <asm/cpu_entry_area.h> /* exception stack */
33#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
34#include <asm/kvm_para.h> /* kvm_handle_async_pf */
35#include <asm/vdso.h> /* fixup_vdso_exception() */
36#include <asm/irq_stack.h>
37#include <asm/fred.h>
38#include <asm/sev.h> /* snp_dump_hva_rmpentry() */
39
40#define CREATE_TRACE_POINTS
41#include <asm/trace/exceptions.h>
42
43/*
44 * Returns 0 if mmiotrace is disabled, or if the fault is not
45 * handled by mmiotrace:
46 */
47static nokprobe_inline int
48kmmio_fault(struct pt_regs *regs, unsigned long addr)
49{
50 if (unlikely(is_kmmio_active()))
51 if (kmmio_handler(regs, addr) == 1)
52 return -1;
53 return 0;
54}
55
56/*
57 * Prefetch quirks:
58 *
59 * 32-bit mode:
60 *
61 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
62 * Check that here and ignore it. This is AMD erratum #91.
63 *
64 * 64-bit mode:
65 *
66 * Sometimes the CPU reports invalid exceptions on prefetch.
67 * Check that here and ignore it.
68 *
69 * Opcode checker based on code by Richard Brunner.
70 */
71static inline int
72check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
73 unsigned char opcode, int *prefetch)
74{
75 unsigned char instr_hi = opcode & 0xf0;
76 unsigned char instr_lo = opcode & 0x0f;
77
78 switch (instr_hi) {
79 case 0x20:
80 case 0x30:
81 /*
82 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
83 * In X86_64 long mode, the CPU will signal invalid
84 * opcode if some of these prefixes are present so
85 * X86_64 will never get here anyway
86 */
87 return ((instr_lo & 7) == 0x6);
88#ifdef CONFIG_X86_64
89 case 0x40:
90 /*
91 * In 64-bit mode 0x40..0x4F are valid REX prefixes
92 */
93 return (!user_mode(regs) || user_64bit_mode(regs));
94#endif
95 case 0x60:
96 /* 0x64 thru 0x67 are valid prefixes in all modes. */
97 return (instr_lo & 0xC) == 0x4;
98 case 0xF0:
99 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
100 return !instr_lo || (instr_lo>>1) == 1;
101 case 0x00:
102 /* Prefetch instruction is 0x0F0D or 0x0F18 */
103 if (get_kernel_nofault(opcode, instr))
104 return 0;
105
106 *prefetch = (instr_lo == 0xF) &&
107 (opcode == 0x0D || opcode == 0x18);
108 return 0;
109 default:
110 return 0;
111 }
112}
113
114static bool is_amd_k8_pre_npt(void)
115{
116 struct cpuinfo_x86 *c = &boot_cpu_data;
117
118 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
119 c->x86_vendor == X86_VENDOR_AMD &&
120 c->x86 == 0xf && c->x86_model < 0x40);
121}
122
123static int
124is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
125{
126 unsigned char *max_instr;
127 unsigned char *instr;
128 int prefetch = 0;
129
130 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
131 if (!is_amd_k8_pre_npt())
132 return 0;
133
134 /*
135 * If it was a exec (instruction fetch) fault on NX page, then
136 * do not ignore the fault:
137 */
138 if (error_code & X86_PF_INSTR)
139 return 0;
140
141 instr = (void *)convert_ip_to_linear(current, regs);
142 max_instr = instr + 15;
143
144 /*
145 * This code has historically always bailed out if IP points to a
146 * not-present page (e.g. due to a race). No one has ever
147 * complained about this.
148 */
149 pagefault_disable();
150
151 while (instr < max_instr) {
152 unsigned char opcode;
153
154 if (user_mode(regs)) {
155 if (get_user(opcode, (unsigned char __user *) instr))
156 break;
157 } else {
158 if (get_kernel_nofault(opcode, instr))
159 break;
160 }
161
162 instr++;
163
164 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
165 break;
166 }
167
168 pagefault_enable();
169 return prefetch;
170}
171
172DEFINE_SPINLOCK(pgd_lock);
173LIST_HEAD(pgd_list);
174
175#ifdef CONFIG_X86_32
176static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
177{
178 unsigned index = pgd_index(address);
179 pgd_t *pgd_k;
180 p4d_t *p4d, *p4d_k;
181 pud_t *pud, *pud_k;
182 pmd_t *pmd, *pmd_k;
183
184 pgd += index;
185 pgd_k = init_mm.pgd + index;
186
187 if (!pgd_present(*pgd_k))
188 return NULL;
189
190 /*
191 * set_pgd(pgd, *pgd_k); here would be useless on PAE
192 * and redundant with the set_pmd() on non-PAE. As would
193 * set_p4d/set_pud.
194 */
195 p4d = p4d_offset(pgd, address);
196 p4d_k = p4d_offset(pgd_k, address);
197 if (!p4d_present(*p4d_k))
198 return NULL;
199
200 pud = pud_offset(p4d, address);
201 pud_k = pud_offset(p4d_k, address);
202 if (!pud_present(*pud_k))
203 return NULL;
204
205 pmd = pmd_offset(pud, address);
206 pmd_k = pmd_offset(pud_k, address);
207
208 if (pmd_present(*pmd) != pmd_present(*pmd_k))
209 set_pmd(pmd, *pmd_k);
210
211 if (!pmd_present(*pmd_k))
212 return NULL;
213 else
214 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
215
216 return pmd_k;
217}
218
219/*
220 * Handle a fault on the vmalloc or module mapping area
221 *
222 * This is needed because there is a race condition between the time
223 * when the vmalloc mapping code updates the PMD to the point in time
224 * where it synchronizes this update with the other page-tables in the
225 * system.
226 *
227 * In this race window another thread/CPU can map an area on the same
228 * PMD, finds it already present and does not synchronize it with the
229 * rest of the system yet. As a result v[mz]alloc might return areas
230 * which are not mapped in every page-table in the system, causing an
231 * unhandled page-fault when they are accessed.
232 */
233static noinline int vmalloc_fault(unsigned long address)
234{
235 unsigned long pgd_paddr;
236 pmd_t *pmd_k;
237 pte_t *pte_k;
238
239 /* Make sure we are in vmalloc area: */
240 if (!(address >= VMALLOC_START && address < VMALLOC_END))
241 return -1;
242
243 /*
244 * Synchronize this task's top level page-table
245 * with the 'reference' page table.
246 *
247 * Do _not_ use "current" here. We might be inside
248 * an interrupt in the middle of a task switch..
249 */
250 pgd_paddr = read_cr3_pa();
251 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
252 if (!pmd_k)
253 return -1;
254
255 if (pmd_leaf(*pmd_k))
256 return 0;
257
258 pte_k = pte_offset_kernel(pmd_k, address);
259 if (!pte_present(*pte_k))
260 return -1;
261
262 return 0;
263}
264NOKPROBE_SYMBOL(vmalloc_fault);
265
266void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
267{
268 unsigned long addr;
269
270 for (addr = start & PMD_MASK;
271 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
272 addr += PMD_SIZE) {
273 struct page *page;
274
275 spin_lock(&pgd_lock);
276 list_for_each_entry(page, &pgd_list, lru) {
277 spinlock_t *pgt_lock;
278
279 /* the pgt_lock only for Xen */
280 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
281
282 spin_lock(pgt_lock);
283 vmalloc_sync_one(page_address(page), addr);
284 spin_unlock(pgt_lock);
285 }
286 spin_unlock(&pgd_lock);
287 }
288}
289
290static bool low_pfn(unsigned long pfn)
291{
292 return pfn < max_low_pfn;
293}
294
295static void dump_pagetable(unsigned long address)
296{
297 pgd_t *base = __va(read_cr3_pa());
298 pgd_t *pgd = &base[pgd_index(address)];
299 p4d_t *p4d;
300 pud_t *pud;
301 pmd_t *pmd;
302 pte_t *pte;
303
304#ifdef CONFIG_X86_PAE
305 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
306 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
307 goto out;
308#define pr_pde pr_cont
309#else
310#define pr_pde pr_info
311#endif
312 p4d = p4d_offset(pgd, address);
313 pud = pud_offset(p4d, address);
314 pmd = pmd_offset(pud, address);
315 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
316#undef pr_pde
317
318 /*
319 * We must not directly access the pte in the highpte
320 * case if the page table is located in highmem.
321 * And let's rather not kmap-atomic the pte, just in case
322 * it's allocated already:
323 */
324 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_leaf(*pmd))
325 goto out;
326
327 pte = pte_offset_kernel(pmd, address);
328 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
329out:
330 pr_cont("\n");
331}
332
333#else /* CONFIG_X86_64: */
334
335#ifdef CONFIG_CPU_SUP_AMD
336static const char errata93_warning[] =
337KERN_ERR
338"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
339"******* Working around it, but it may cause SEGVs or burn power.\n"
340"******* Please consider a BIOS update.\n"
341"******* Disabling USB legacy in the BIOS may also help.\n";
342#endif
343
344static int bad_address(void *p)
345{
346 unsigned long dummy;
347
348 return get_kernel_nofault(dummy, (unsigned long *)p);
349}
350
351static void dump_pagetable(unsigned long address)
352{
353 pgd_t *base = __va(read_cr3_pa());
354 pgd_t *pgd = base + pgd_index(address);
355 p4d_t *p4d;
356 pud_t *pud;
357 pmd_t *pmd;
358 pte_t *pte;
359
360 if (bad_address(pgd))
361 goto bad;
362
363 pr_info("PGD %lx ", pgd_val(*pgd));
364
365 if (!pgd_present(*pgd))
366 goto out;
367
368 p4d = p4d_offset(pgd, address);
369 if (bad_address(p4d))
370 goto bad;
371
372 pr_cont("P4D %lx ", p4d_val(*p4d));
373 if (!p4d_present(*p4d) || p4d_leaf(*p4d))
374 goto out;
375
376 pud = pud_offset(p4d, address);
377 if (bad_address(pud))
378 goto bad;
379
380 pr_cont("PUD %lx ", pud_val(*pud));
381 if (!pud_present(*pud) || pud_leaf(*pud))
382 goto out;
383
384 pmd = pmd_offset(pud, address);
385 if (bad_address(pmd))
386 goto bad;
387
388 pr_cont("PMD %lx ", pmd_val(*pmd));
389 if (!pmd_present(*pmd) || pmd_leaf(*pmd))
390 goto out;
391
392 pte = pte_offset_kernel(pmd, address);
393 if (bad_address(pte))
394 goto bad;
395
396 pr_cont("PTE %lx", pte_val(*pte));
397out:
398 pr_cont("\n");
399 return;
400bad:
401 pr_info("BAD\n");
402}
403
404#endif /* CONFIG_X86_64 */
405
406/*
407 * Workaround for K8 erratum #93 & buggy BIOS.
408 *
409 * BIOS SMM functions are required to use a specific workaround
410 * to avoid corruption of the 64bit RIP register on C stepping K8.
411 *
412 * A lot of BIOS that didn't get tested properly miss this.
413 *
414 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
415 * Try to work around it here.
416 *
417 * Note we only handle faults in kernel here.
418 * Does nothing on 32-bit.
419 */
420static int is_errata93(struct pt_regs *regs, unsigned long address)
421{
422#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
423 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
424 || boot_cpu_data.x86 != 0xf)
425 return 0;
426
427 if (user_mode(regs))
428 return 0;
429
430 if (address != regs->ip)
431 return 0;
432
433 if ((address >> 32) != 0)
434 return 0;
435
436 address |= 0xffffffffUL << 32;
437 if ((address >= (u64)_stext && address <= (u64)_etext) ||
438 (address >= MODULES_VADDR && address <= MODULES_END)) {
439 printk_once(errata93_warning);
440 regs->ip = address;
441 return 1;
442 }
443#endif
444 return 0;
445}
446
447/*
448 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
449 * to illegal addresses >4GB.
450 *
451 * We catch this in the page fault handler because these addresses
452 * are not reachable. Just detect this case and return. Any code
453 * segment in LDT is compatibility mode.
454 */
455static int is_errata100(struct pt_regs *regs, unsigned long address)
456{
457#ifdef CONFIG_X86_64
458 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
459 return 1;
460#endif
461 return 0;
462}
463
464/* Pentium F0 0F C7 C8 bug workaround: */
465static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
466 unsigned long address)
467{
468#ifdef CONFIG_X86_F00F_BUG
469 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
470 idt_is_f00f_address(address)) {
471 handle_invalid_op(regs);
472 return 1;
473 }
474#endif
475 return 0;
476}
477
478static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
479{
480 u32 offset = (index >> 3) * sizeof(struct desc_struct);
481 unsigned long addr;
482 struct ldttss_desc desc;
483
484 if (index == 0) {
485 pr_alert("%s: NULL\n", name);
486 return;
487 }
488
489 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
490 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
491 return;
492 }
493
494 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
495 sizeof(struct ldttss_desc))) {
496 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
497 name, index);
498 return;
499 }
500
501 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
502#ifdef CONFIG_X86_64
503 addr |= ((u64)desc.base3 << 32);
504#endif
505 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
506 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
507}
508
509static void
510show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
511{
512 if (!oops_may_print())
513 return;
514
515 if (error_code & X86_PF_INSTR) {
516 unsigned int level;
517 pgd_t *pgd;
518 pte_t *pte;
519
520 pgd = __va(read_cr3_pa());
521 pgd += pgd_index(address);
522
523 pte = lookup_address_in_pgd(pgd, address, &level);
524
525 if (pte && pte_present(*pte) && !pte_exec(*pte))
526 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
527 from_kuid(&init_user_ns, current_uid()));
528 if (pte && pte_present(*pte) && pte_exec(*pte) &&
529 (pgd_flags(*pgd) & _PAGE_USER) &&
530 (__read_cr4() & X86_CR4_SMEP))
531 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
532 from_kuid(&init_user_ns, current_uid()));
533 }
534
535 if (address < PAGE_SIZE && !user_mode(regs))
536 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
537 (void *)address);
538 else
539 pr_alert("BUG: unable to handle page fault for address: %px\n",
540 (void *)address);
541
542 pr_alert("#PF: %s %s in %s mode\n",
543 (error_code & X86_PF_USER) ? "user" : "supervisor",
544 (error_code & X86_PF_INSTR) ? "instruction fetch" :
545 (error_code & X86_PF_WRITE) ? "write access" :
546 "read access",
547 user_mode(regs) ? "user" : "kernel");
548 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
549 !(error_code & X86_PF_PROT) ? "not-present page" :
550 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
551 (error_code & X86_PF_PK) ? "protection keys violation" :
552 (error_code & X86_PF_RMP) ? "RMP violation" :
553 "permissions violation");
554
555 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
556 struct desc_ptr idt, gdt;
557 u16 ldtr, tr;
558
559 /*
560 * This can happen for quite a few reasons. The more obvious
561 * ones are faults accessing the GDT, or LDT. Perhaps
562 * surprisingly, if the CPU tries to deliver a benign or
563 * contributory exception from user code and gets a page fault
564 * during delivery, the page fault can be delivered as though
565 * it originated directly from user code. This could happen
566 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
567 * kernel or IST stack.
568 */
569 store_idt(&idt);
570
571 /* Usable even on Xen PV -- it's just slow. */
572 native_store_gdt(&gdt);
573
574 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
575 idt.address, idt.size, gdt.address, gdt.size);
576
577 store_ldt(ldtr);
578 show_ldttss(&gdt, "LDTR", ldtr);
579
580 store_tr(tr);
581 show_ldttss(&gdt, "TR", tr);
582 }
583
584 dump_pagetable(address);
585
586 if (error_code & X86_PF_RMP)
587 snp_dump_hva_rmpentry(address);
588}
589
590static noinline void
591pgtable_bad(struct pt_regs *regs, unsigned long error_code,
592 unsigned long address)
593{
594 struct task_struct *tsk;
595 unsigned long flags;
596 int sig;
597
598 flags = oops_begin();
599 tsk = current;
600 sig = SIGKILL;
601
602 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
603 tsk->comm, address);
604 dump_pagetable(address);
605
606 if (__die("Bad pagetable", regs, error_code))
607 sig = 0;
608
609 oops_end(flags, regs, sig);
610}
611
612static void sanitize_error_code(unsigned long address,
613 unsigned long *error_code)
614{
615 /*
616 * To avoid leaking information about the kernel page
617 * table layout, pretend that user-mode accesses to
618 * kernel addresses are always protection faults.
619 *
620 * NB: This means that failed vsyscalls with vsyscall=none
621 * will have the PROT bit. This doesn't leak any
622 * information and does not appear to cause any problems.
623 */
624 if (address >= TASK_SIZE_MAX)
625 *error_code |= X86_PF_PROT;
626}
627
628static void set_signal_archinfo(unsigned long address,
629 unsigned long error_code)
630{
631 struct task_struct *tsk = current;
632
633 tsk->thread.trap_nr = X86_TRAP_PF;
634 tsk->thread.error_code = error_code | X86_PF_USER;
635 tsk->thread.cr2 = address;
636}
637
638static noinline void
639page_fault_oops(struct pt_regs *regs, unsigned long error_code,
640 unsigned long address)
641{
642#ifdef CONFIG_VMAP_STACK
643 struct stack_info info;
644#endif
645 unsigned long flags;
646 int sig;
647
648 if (user_mode(regs)) {
649 /*
650 * Implicit kernel access from user mode? Skip the stack
651 * overflow and EFI special cases.
652 */
653 goto oops;
654 }
655
656#ifdef CONFIG_VMAP_STACK
657 /*
658 * Stack overflow? During boot, we can fault near the initial
659 * stack in the direct map, but that's not an overflow -- check
660 * that we're in vmalloc space to avoid this.
661 */
662 if (is_vmalloc_addr((void *)address) &&
663 get_stack_guard_info((void *)address, &info)) {
664 /*
665 * We're likely to be running with very little stack space
666 * left. It's plausible that we'd hit this condition but
667 * double-fault even before we get this far, in which case
668 * we're fine: the double-fault handler will deal with it.
669 *
670 * We don't want to make it all the way into the oops code
671 * and then double-fault, though, because we're likely to
672 * break the console driver and lose most of the stack dump.
673 */
674 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
675 handle_stack_overflow,
676 ASM_CALL_ARG3,
677 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
678
679 unreachable();
680 }
681#endif
682
683 /*
684 * Buggy firmware could access regions which might page fault. If
685 * this happens, EFI has a special OOPS path that will try to
686 * avoid hanging the system.
687 */
688 if (IS_ENABLED(CONFIG_EFI))
689 efi_crash_gracefully_on_page_fault(address);
690
691 /* Only not-present faults should be handled by KFENCE. */
692 if (!(error_code & X86_PF_PROT) &&
693 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
694 return;
695
696oops:
697 /*
698 * Oops. The kernel tried to access some bad page. We'll have to
699 * terminate things with extreme prejudice:
700 */
701 flags = oops_begin();
702
703 show_fault_oops(regs, error_code, address);
704
705 if (task_stack_end_corrupted(current))
706 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
707
708 sig = SIGKILL;
709 if (__die("Oops", regs, error_code))
710 sig = 0;
711
712 /* Executive summary in case the body of the oops scrolled away */
713 printk(KERN_DEFAULT "CR2: %016lx\n", address);
714
715 oops_end(flags, regs, sig);
716}
717
718static noinline void
719kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
720 unsigned long address, int signal, int si_code,
721 u32 pkey)
722{
723 WARN_ON_ONCE(user_mode(regs));
724
725 /* Are we prepared to handle this kernel fault? */
726 if (fixup_exception(regs, X86_TRAP_PF, error_code, address))
727 return;
728
729 /*
730 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
731 * instruction.
732 */
733 if (is_prefetch(regs, error_code, address))
734 return;
735
736 page_fault_oops(regs, error_code, address);
737}
738
739/*
740 * Print out info about fatal segfaults, if the show_unhandled_signals
741 * sysctl is set:
742 */
743static inline void
744show_signal_msg(struct pt_regs *regs, unsigned long error_code,
745 unsigned long address, struct task_struct *tsk)
746{
747 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
748 /* This is a racy snapshot, but it's better than nothing. */
749 int cpu = raw_smp_processor_id();
750
751 if (!unhandled_signal(tsk, SIGSEGV))
752 return;
753
754 if (!printk_ratelimit())
755 return;
756
757 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
758 loglvl, tsk->comm, task_pid_nr(tsk), address,
759 (void *)regs->ip, (void *)regs->sp, error_code);
760
761 print_vma_addr(KERN_CONT " in ", regs->ip);
762
763 /*
764 * Dump the likely CPU where the fatal segfault happened.
765 * This can help identify faulty hardware.
766 */
767 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
768 topology_core_id(cpu), topology_physical_package_id(cpu));
769
770
771 printk(KERN_CONT "\n");
772
773 show_opcodes(regs, loglvl);
774}
775
776static void
777__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
778 unsigned long address, u32 pkey, int si_code)
779{
780 struct task_struct *tsk = current;
781
782 if (!user_mode(regs)) {
783 kernelmode_fixup_or_oops(regs, error_code, address,
784 SIGSEGV, si_code, pkey);
785 return;
786 }
787
788 if (!(error_code & X86_PF_USER)) {
789 /* Implicit user access to kernel memory -- just oops */
790 page_fault_oops(regs, error_code, address);
791 return;
792 }
793
794 /*
795 * User mode accesses just cause a SIGSEGV.
796 * It's possible to have interrupts off here:
797 */
798 local_irq_enable();
799
800 /*
801 * Valid to do another page fault here because this one came
802 * from user space:
803 */
804 if (is_prefetch(regs, error_code, address))
805 return;
806
807 if (is_errata100(regs, address))
808 return;
809
810 sanitize_error_code(address, &error_code);
811
812 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
813 return;
814
815 if (likely(show_unhandled_signals))
816 show_signal_msg(regs, error_code, address, tsk);
817
818 set_signal_archinfo(address, error_code);
819
820 if (si_code == SEGV_PKUERR)
821 force_sig_pkuerr((void __user *)address, pkey);
822 else
823 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
824
825 local_irq_disable();
826}
827
828static noinline void
829bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
830 unsigned long address)
831{
832 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
833}
834
835static void
836__bad_area(struct pt_regs *regs, unsigned long error_code,
837 unsigned long address, u32 pkey, int si_code)
838{
839 struct mm_struct *mm = current->mm;
840 /*
841 * Something tried to access memory that isn't in our memory map..
842 * Fix it, but check if it's kernel or user first..
843 */
844 mmap_read_unlock(mm);
845
846 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
847}
848
849static inline bool bad_area_access_from_pkeys(unsigned long error_code,
850 struct vm_area_struct *vma)
851{
852 /* This code is always called on the current mm */
853 bool foreign = false;
854
855 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
856 return false;
857 if (error_code & X86_PF_PK)
858 return true;
859 /* this checks permission keys on the VMA: */
860 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
861 (error_code & X86_PF_INSTR), foreign))
862 return true;
863 return false;
864}
865
866static noinline void
867bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
868 unsigned long address, struct vm_area_struct *vma)
869{
870 /*
871 * This OSPKE check is not strictly necessary at runtime.
872 * But, doing it this way allows compiler optimizations
873 * if pkeys are compiled out.
874 */
875 if (bad_area_access_from_pkeys(error_code, vma)) {
876 /*
877 * A protection key fault means that the PKRU value did not allow
878 * access to some PTE. Userspace can figure out what PKRU was
879 * from the XSAVE state. This function captures the pkey from
880 * the vma and passes it to userspace so userspace can discover
881 * which protection key was set on the PTE.
882 *
883 * If we get here, we know that the hardware signaled a X86_PF_PK
884 * fault and that there was a VMA once we got in the fault
885 * handler. It does *not* guarantee that the VMA we find here
886 * was the one that we faulted on.
887 *
888 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
889 * 2. T1 : set PKRU to deny access to pkey=4, touches page
890 * 3. T1 : faults...
891 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
892 * 5. T1 : enters fault handler, takes mmap_lock, etc...
893 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
894 * faulted on a pte with its pkey=4.
895 */
896 u32 pkey = vma_pkey(vma);
897
898 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
899 } else {
900 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
901 }
902}
903
904static void
905do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
906 vm_fault_t fault)
907{
908 /* Kernel mode? Handle exceptions or die: */
909 if (!user_mode(regs)) {
910 kernelmode_fixup_or_oops(regs, error_code, address,
911 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
912 return;
913 }
914
915 /* User-space => ok to do another page fault: */
916 if (is_prefetch(regs, error_code, address))
917 return;
918
919 sanitize_error_code(address, &error_code);
920
921 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
922 return;
923
924 set_signal_archinfo(address, error_code);
925
926#ifdef CONFIG_MEMORY_FAILURE
927 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
928 struct task_struct *tsk = current;
929 unsigned lsb = 0;
930
931 pr_err(
932 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
933 tsk->comm, tsk->pid, address);
934 if (fault & VM_FAULT_HWPOISON_LARGE)
935 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
936 if (fault & VM_FAULT_HWPOISON)
937 lsb = PAGE_SHIFT;
938 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
939 return;
940 }
941#endif
942 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
943}
944
945static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
946{
947 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
948 return 0;
949
950 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
951 return 0;
952
953 return 1;
954}
955
956/*
957 * Handle a spurious fault caused by a stale TLB entry.
958 *
959 * This allows us to lazily refresh the TLB when increasing the
960 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
961 * eagerly is very expensive since that implies doing a full
962 * cross-processor TLB flush, even if no stale TLB entries exist
963 * on other processors.
964 *
965 * Spurious faults may only occur if the TLB contains an entry with
966 * fewer permission than the page table entry. Non-present (P = 0)
967 * and reserved bit (R = 1) faults are never spurious.
968 *
969 * There are no security implications to leaving a stale TLB when
970 * increasing the permissions on a page.
971 *
972 * Returns non-zero if a spurious fault was handled, zero otherwise.
973 *
974 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
975 * (Optional Invalidation).
976 */
977static noinline int
978spurious_kernel_fault(unsigned long error_code, unsigned long address)
979{
980 pgd_t *pgd;
981 p4d_t *p4d;
982 pud_t *pud;
983 pmd_t *pmd;
984 pte_t *pte;
985 int ret;
986
987 /*
988 * Only writes to RO or instruction fetches from NX may cause
989 * spurious faults.
990 *
991 * These could be from user or supervisor accesses but the TLB
992 * is only lazily flushed after a kernel mapping protection
993 * change, so user accesses are not expected to cause spurious
994 * faults.
995 */
996 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
997 error_code != (X86_PF_INSTR | X86_PF_PROT))
998 return 0;
999
1000 pgd = init_mm.pgd + pgd_index(address);
1001 if (!pgd_present(*pgd))
1002 return 0;
1003
1004 p4d = p4d_offset(pgd, address);
1005 if (!p4d_present(*p4d))
1006 return 0;
1007
1008 if (p4d_leaf(*p4d))
1009 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1010
1011 pud = pud_offset(p4d, address);
1012 if (!pud_present(*pud))
1013 return 0;
1014
1015 if (pud_leaf(*pud))
1016 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1017
1018 pmd = pmd_offset(pud, address);
1019 if (!pmd_present(*pmd))
1020 return 0;
1021
1022 if (pmd_leaf(*pmd))
1023 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1024
1025 pte = pte_offset_kernel(pmd, address);
1026 if (!pte_present(*pte))
1027 return 0;
1028
1029 ret = spurious_kernel_fault_check(error_code, pte);
1030 if (!ret)
1031 return 0;
1032
1033 /*
1034 * Make sure we have permissions in PMD.
1035 * If not, then there's a bug in the page tables:
1036 */
1037 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1038 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1039
1040 return ret;
1041}
1042NOKPROBE_SYMBOL(spurious_kernel_fault);
1043
1044int show_unhandled_signals = 1;
1045
1046static inline int
1047access_error(unsigned long error_code, struct vm_area_struct *vma)
1048{
1049 /* This is only called for the current mm, so: */
1050 bool foreign = false;
1051
1052 /*
1053 * Read or write was blocked by protection keys. This is
1054 * always an unconditional error and can never result in
1055 * a follow-up action to resolve the fault, like a COW.
1056 */
1057 if (error_code & X86_PF_PK)
1058 return 1;
1059
1060 /*
1061 * SGX hardware blocked the access. This usually happens
1062 * when the enclave memory contents have been destroyed, like
1063 * after a suspend/resume cycle. In any case, the kernel can't
1064 * fix the cause of the fault. Handle the fault as an access
1065 * error even in cases where no actual access violation
1066 * occurred. This allows userspace to rebuild the enclave in
1067 * response to the signal.
1068 */
1069 if (unlikely(error_code & X86_PF_SGX))
1070 return 1;
1071
1072 /*
1073 * Make sure to check the VMA so that we do not perform
1074 * faults just to hit a X86_PF_PK as soon as we fill in a
1075 * page.
1076 */
1077 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1078 (error_code & X86_PF_INSTR), foreign))
1079 return 1;
1080
1081 /*
1082 * Shadow stack accesses (PF_SHSTK=1) are only permitted to
1083 * shadow stack VMAs. All other accesses result in an error.
1084 */
1085 if (error_code & X86_PF_SHSTK) {
1086 if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK)))
1087 return 1;
1088 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1089 return 1;
1090 return 0;
1091 }
1092
1093 if (error_code & X86_PF_WRITE) {
1094 /* write, present and write, not present: */
1095 if (unlikely(vma->vm_flags & VM_SHADOW_STACK))
1096 return 1;
1097 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1098 return 1;
1099 return 0;
1100 }
1101
1102 /* read, present: */
1103 if (unlikely(error_code & X86_PF_PROT))
1104 return 1;
1105
1106 /* read, not present: */
1107 if (unlikely(!vma_is_accessible(vma)))
1108 return 1;
1109
1110 return 0;
1111}
1112
1113bool fault_in_kernel_space(unsigned long address)
1114{
1115 /*
1116 * On 64-bit systems, the vsyscall page is at an address above
1117 * TASK_SIZE_MAX, but is not considered part of the kernel
1118 * address space.
1119 */
1120 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1121 return false;
1122
1123 return address >= TASK_SIZE_MAX;
1124}
1125
1126/*
1127 * Called for all faults where 'address' is part of the kernel address
1128 * space. Might get called for faults that originate from *code* that
1129 * ran in userspace or the kernel.
1130 */
1131static void
1132do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1133 unsigned long address)
1134{
1135 /*
1136 * Protection keys exceptions only happen on user pages. We
1137 * have no user pages in the kernel portion of the address
1138 * space, so do not expect them here.
1139 */
1140 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1141
1142#ifdef CONFIG_X86_32
1143 /*
1144 * We can fault-in kernel-space virtual memory on-demand. The
1145 * 'reference' page table is init_mm.pgd.
1146 *
1147 * NOTE! We MUST NOT take any locks for this case. We may
1148 * be in an interrupt or a critical region, and should
1149 * only copy the information from the master page table,
1150 * nothing more.
1151 *
1152 * Before doing this on-demand faulting, ensure that the
1153 * fault is not any of the following:
1154 * 1. A fault on a PTE with a reserved bit set.
1155 * 2. A fault caused by a user-mode access. (Do not demand-
1156 * fault kernel memory due to user-mode accesses).
1157 * 3. A fault caused by a page-level protection violation.
1158 * (A demand fault would be on a non-present page which
1159 * would have X86_PF_PROT==0).
1160 *
1161 * This is only needed to close a race condition on x86-32 in
1162 * the vmalloc mapping/unmapping code. See the comment above
1163 * vmalloc_fault() for details. On x86-64 the race does not
1164 * exist as the vmalloc mappings don't need to be synchronized
1165 * there.
1166 */
1167 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1168 if (vmalloc_fault(address) >= 0)
1169 return;
1170 }
1171#endif
1172
1173 if (is_f00f_bug(regs, hw_error_code, address))
1174 return;
1175
1176 /* Was the fault spurious, caused by lazy TLB invalidation? */
1177 if (spurious_kernel_fault(hw_error_code, address))
1178 return;
1179
1180 /* kprobes don't want to hook the spurious faults: */
1181 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1182 return;
1183
1184 /*
1185 * Note, despite being a "bad area", there are quite a few
1186 * acceptable reasons to get here, such as erratum fixups
1187 * and handling kernel code that can fault, like get_user().
1188 *
1189 * Don't take the mm semaphore here. If we fixup a prefetch
1190 * fault we could otherwise deadlock:
1191 */
1192 bad_area_nosemaphore(regs, hw_error_code, address);
1193}
1194NOKPROBE_SYMBOL(do_kern_addr_fault);
1195
1196/*
1197 * Handle faults in the user portion of the address space. Nothing in here
1198 * should check X86_PF_USER without a specific justification: for almost
1199 * all purposes, we should treat a normal kernel access to user memory
1200 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1201 * The one exception is AC flag handling, which is, per the x86
1202 * architecture, special for WRUSS.
1203 */
1204static inline
1205void do_user_addr_fault(struct pt_regs *regs,
1206 unsigned long error_code,
1207 unsigned long address)
1208{
1209 struct vm_area_struct *vma;
1210 struct task_struct *tsk;
1211 struct mm_struct *mm;
1212 vm_fault_t fault;
1213 unsigned int flags = FAULT_FLAG_DEFAULT;
1214
1215 tsk = current;
1216 mm = tsk->mm;
1217
1218 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1219 /*
1220 * Whoops, this is kernel mode code trying to execute from
1221 * user memory. Unless this is AMD erratum #93, which
1222 * corrupts RIP such that it looks like a user address,
1223 * this is unrecoverable. Don't even try to look up the
1224 * VMA or look for extable entries.
1225 */
1226 if (is_errata93(regs, address))
1227 return;
1228
1229 page_fault_oops(regs, error_code, address);
1230 return;
1231 }
1232
1233 /* kprobes don't want to hook the spurious faults: */
1234 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1235 return;
1236
1237 /*
1238 * Reserved bits are never expected to be set on
1239 * entries in the user portion of the page tables.
1240 */
1241 if (unlikely(error_code & X86_PF_RSVD))
1242 pgtable_bad(regs, error_code, address);
1243
1244 /*
1245 * If SMAP is on, check for invalid kernel (supervisor) access to user
1246 * pages in the user address space. The odd case here is WRUSS,
1247 * which, according to the preliminary documentation, does not respect
1248 * SMAP and will have the USER bit set so, in all cases, SMAP
1249 * enforcement appears to be consistent with the USER bit.
1250 */
1251 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1252 !(error_code & X86_PF_USER) &&
1253 !(regs->flags & X86_EFLAGS_AC))) {
1254 /*
1255 * No extable entry here. This was a kernel access to an
1256 * invalid pointer. get_kernel_nofault() will not get here.
1257 */
1258 page_fault_oops(regs, error_code, address);
1259 return;
1260 }
1261
1262 /*
1263 * If we're in an interrupt, have no user context or are running
1264 * in a region with pagefaults disabled then we must not take the fault
1265 */
1266 if (unlikely(faulthandler_disabled() || !mm)) {
1267 bad_area_nosemaphore(regs, error_code, address);
1268 return;
1269 }
1270
1271 /* Legacy check - remove this after verifying that it doesn't trigger */
1272 if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) {
1273 bad_area_nosemaphore(regs, error_code, address);
1274 return;
1275 }
1276
1277 local_irq_enable();
1278
1279 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1280
1281 /*
1282 * Read-only permissions can not be expressed in shadow stack PTEs.
1283 * Treat all shadow stack accesses as WRITE faults. This ensures
1284 * that the MM will prepare everything (e.g., break COW) such that
1285 * maybe_mkwrite() can create a proper shadow stack PTE.
1286 */
1287 if (error_code & X86_PF_SHSTK)
1288 flags |= FAULT_FLAG_WRITE;
1289 if (error_code & X86_PF_WRITE)
1290 flags |= FAULT_FLAG_WRITE;
1291 if (error_code & X86_PF_INSTR)
1292 flags |= FAULT_FLAG_INSTRUCTION;
1293
1294 /*
1295 * We set FAULT_FLAG_USER based on the register state, not
1296 * based on X86_PF_USER. User space accesses that cause
1297 * system page faults are still user accesses.
1298 */
1299 if (user_mode(regs))
1300 flags |= FAULT_FLAG_USER;
1301
1302#ifdef CONFIG_X86_64
1303 /*
1304 * Faults in the vsyscall page might need emulation. The
1305 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1306 * considered to be part of the user address space.
1307 *
1308 * The vsyscall page does not have a "real" VMA, so do this
1309 * emulation before we go searching for VMAs.
1310 *
1311 * PKRU never rejects instruction fetches, so we don't need
1312 * to consider the PF_PK bit.
1313 */
1314 if (is_vsyscall_vaddr(address)) {
1315 if (emulate_vsyscall(error_code, regs, address))
1316 return;
1317 }
1318#endif
1319
1320 if (!(flags & FAULT_FLAG_USER))
1321 goto lock_mmap;
1322
1323 vma = lock_vma_under_rcu(mm, address);
1324 if (!vma)
1325 goto lock_mmap;
1326
1327 if (unlikely(access_error(error_code, vma))) {
1328 vma_end_read(vma);
1329 goto lock_mmap;
1330 }
1331 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
1332 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
1333 vma_end_read(vma);
1334
1335 if (!(fault & VM_FAULT_RETRY)) {
1336 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
1337 goto done;
1338 }
1339 count_vm_vma_lock_event(VMA_LOCK_RETRY);
1340 if (fault & VM_FAULT_MAJOR)
1341 flags |= FAULT_FLAG_TRIED;
1342
1343 /* Quick path to respond to signals */
1344 if (fault_signal_pending(fault, regs)) {
1345 if (!user_mode(regs))
1346 kernelmode_fixup_or_oops(regs, error_code, address,
1347 SIGBUS, BUS_ADRERR,
1348 ARCH_DEFAULT_PKEY);
1349 return;
1350 }
1351lock_mmap:
1352
1353retry:
1354 vma = lock_mm_and_find_vma(mm, address, regs);
1355 if (unlikely(!vma)) {
1356 bad_area_nosemaphore(regs, error_code, address);
1357 return;
1358 }
1359
1360 /*
1361 * Ok, we have a good vm_area for this memory access, so
1362 * we can handle it..
1363 */
1364 if (unlikely(access_error(error_code, vma))) {
1365 bad_area_access_error(regs, error_code, address, vma);
1366 return;
1367 }
1368
1369 /*
1370 * If for any reason at all we couldn't handle the fault,
1371 * make sure we exit gracefully rather than endlessly redo
1372 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1373 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1374 *
1375 * Note that handle_userfault() may also release and reacquire mmap_lock
1376 * (and not return with VM_FAULT_RETRY), when returning to userland to
1377 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1378 * (potentially after handling any pending signal during the return to
1379 * userland). The return to userland is identified whenever
1380 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1381 */
1382 fault = handle_mm_fault(vma, address, flags, regs);
1383
1384 if (fault_signal_pending(fault, regs)) {
1385 /*
1386 * Quick path to respond to signals. The core mm code
1387 * has unlocked the mm for us if we get here.
1388 */
1389 if (!user_mode(regs))
1390 kernelmode_fixup_or_oops(regs, error_code, address,
1391 SIGBUS, BUS_ADRERR,
1392 ARCH_DEFAULT_PKEY);
1393 return;
1394 }
1395
1396 /* The fault is fully completed (including releasing mmap lock) */
1397 if (fault & VM_FAULT_COMPLETED)
1398 return;
1399
1400 /*
1401 * If we need to retry the mmap_lock has already been released,
1402 * and if there is a fatal signal pending there is no guarantee
1403 * that we made any progress. Handle this case first.
1404 */
1405 if (unlikely(fault & VM_FAULT_RETRY)) {
1406 flags |= FAULT_FLAG_TRIED;
1407 goto retry;
1408 }
1409
1410 mmap_read_unlock(mm);
1411done:
1412 if (likely(!(fault & VM_FAULT_ERROR)))
1413 return;
1414
1415 if (fatal_signal_pending(current) && !user_mode(regs)) {
1416 kernelmode_fixup_or_oops(regs, error_code, address,
1417 0, 0, ARCH_DEFAULT_PKEY);
1418 return;
1419 }
1420
1421 if (fault & VM_FAULT_OOM) {
1422 /* Kernel mode? Handle exceptions or die: */
1423 if (!user_mode(regs)) {
1424 kernelmode_fixup_or_oops(regs, error_code, address,
1425 SIGSEGV, SEGV_MAPERR,
1426 ARCH_DEFAULT_PKEY);
1427 return;
1428 }
1429
1430 /*
1431 * We ran out of memory, call the OOM killer, and return the
1432 * userspace (which will retry the fault, or kill us if we got
1433 * oom-killed):
1434 */
1435 pagefault_out_of_memory();
1436 } else {
1437 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1438 VM_FAULT_HWPOISON_LARGE))
1439 do_sigbus(regs, error_code, address, fault);
1440 else if (fault & VM_FAULT_SIGSEGV)
1441 bad_area_nosemaphore(regs, error_code, address);
1442 else
1443 BUG();
1444 }
1445}
1446NOKPROBE_SYMBOL(do_user_addr_fault);
1447
1448static __always_inline void
1449trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1450 unsigned long address)
1451{
1452 if (!trace_pagefault_enabled())
1453 return;
1454
1455 if (user_mode(regs))
1456 trace_page_fault_user(address, regs, error_code);
1457 else
1458 trace_page_fault_kernel(address, regs, error_code);
1459}
1460
1461static __always_inline void
1462handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1463 unsigned long address)
1464{
1465 trace_page_fault_entries(regs, error_code, address);
1466
1467 if (unlikely(kmmio_fault(regs, address)))
1468 return;
1469
1470 /* Was the fault on kernel-controlled part of the address space? */
1471 if (unlikely(fault_in_kernel_space(address))) {
1472 do_kern_addr_fault(regs, error_code, address);
1473 } else {
1474 do_user_addr_fault(regs, error_code, address);
1475 /*
1476 * User address page fault handling might have reenabled
1477 * interrupts. Fixing up all potential exit points of
1478 * do_user_addr_fault() and its leaf functions is just not
1479 * doable w/o creating an unholy mess or turning the code
1480 * upside down.
1481 */
1482 local_irq_disable();
1483 }
1484}
1485
1486DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1487{
1488 irqentry_state_t state;
1489 unsigned long address;
1490
1491 address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2();
1492
1493 prefetchw(¤t->mm->mmap_lock);
1494
1495 /*
1496 * KVM uses #PF vector to deliver 'page not present' events to guests
1497 * (asynchronous page fault mechanism). The event happens when a
1498 * userspace task is trying to access some valid (from guest's point of
1499 * view) memory which is not currently mapped by the host (e.g. the
1500 * memory is swapped out). Note, the corresponding "page ready" event
1501 * which is injected when the memory becomes available, is delivered via
1502 * an interrupt mechanism and not a #PF exception
1503 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1504 *
1505 * We are relying on the interrupted context being sane (valid RSP,
1506 * relevant locks not held, etc.), which is fine as long as the
1507 * interrupted context had IF=1. We are also relying on the KVM
1508 * async pf type field and CR2 being read consistently instead of
1509 * getting values from real and async page faults mixed up.
1510 *
1511 * Fingers crossed.
1512 *
1513 * The async #PF handling code takes care of idtentry handling
1514 * itself.
1515 */
1516 if (kvm_handle_async_pf(regs, (u32)address))
1517 return;
1518
1519 /*
1520 * Entry handling for valid #PF from kernel mode is slightly
1521 * different: RCU is already watching and ct_irq_enter() must not
1522 * be invoked because a kernel fault on a user space address might
1523 * sleep.
1524 *
1525 * In case the fault hit a RCU idle region the conditional entry
1526 * code reenabled RCU to avoid subsequent wreckage which helps
1527 * debuggability.
1528 */
1529 state = irqentry_enter(regs);
1530
1531 instrumentation_begin();
1532 handle_page_fault(regs, error_code, address);
1533 instrumentation_end();
1534
1535 irqentry_exit(regs, state);
1536}