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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PowerPC version
4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
5 *
6 * Derived from "arch/i386/mm/fault.c"
7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 *
9 * Modified by Cort Dougan and Paul Mackerras.
10 *
11 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
12 */
13
14#include <linux/signal.h>
15#include <linux/sched.h>
16#include <linux/sched/task_stack.h>
17#include <linux/kernel.h>
18#include <linux/errno.h>
19#include <linux/string.h>
20#include <linux/types.h>
21#include <linux/pagemap.h>
22#include <linux/ptrace.h>
23#include <linux/mman.h>
24#include <linux/mm.h>
25#include <linux/interrupt.h>
26#include <linux/highmem.h>
27#include <linux/extable.h>
28#include <linux/kprobes.h>
29#include <linux/kdebug.h>
30#include <linux/perf_event.h>
31#include <linux/ratelimit.h>
32#include <linux/context_tracking.h>
33#include <linux/hugetlb.h>
34#include <linux/uaccess.h>
35#include <linux/kfence.h>
36#include <linux/pkeys.h>
37
38#include <asm/firmware.h>
39#include <asm/interrupt.h>
40#include <asm/page.h>
41#include <asm/mmu.h>
42#include <asm/mmu_context.h>
43#include <asm/siginfo.h>
44#include <asm/debug.h>
45#include <asm/kup.h>
46#include <asm/inst.h>
47
48
49/*
50 * do_page_fault error handling helpers
51 */
52
53static int
54__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
55{
56 /*
57 * If we are in kernel mode, bail out with a SEGV, this will
58 * be caught by the assembly which will restore the non-volatile
59 * registers before calling bad_page_fault()
60 */
61 if (!user_mode(regs))
62 return SIGSEGV;
63
64 _exception(SIGSEGV, regs, si_code, address);
65
66 return 0;
67}
68
69static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
70{
71 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
72}
73
74static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
75{
76 struct mm_struct *mm = current->mm;
77
78 /*
79 * Something tried to access memory that isn't in our memory map..
80 * Fix it, but check if it's kernel or user first..
81 */
82 mmap_read_unlock(mm);
83
84 return __bad_area_nosemaphore(regs, address, si_code);
85}
86
87static noinline int bad_area(struct pt_regs *regs, unsigned long address)
88{
89 return __bad_area(regs, address, SEGV_MAPERR);
90}
91
92static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
93 struct vm_area_struct *vma)
94{
95 struct mm_struct *mm = current->mm;
96 int pkey;
97
98 /*
99 * We don't try to fetch the pkey from page table because reading
100 * page table without locking doesn't guarantee stable pte value.
101 * Hence the pkey value that we return to userspace can be different
102 * from the pkey that actually caused access error.
103 *
104 * It does *not* guarantee that the VMA we find here
105 * was the one that we faulted on.
106 *
107 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
108 * 2. T1 : set AMR to deny access to pkey=4, touches, page
109 * 3. T1 : faults...
110 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
111 * 5. T1 : enters fault handler, takes mmap_lock, etc...
112 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
113 * faulted on a pte with its pkey=4.
114 */
115 pkey = vma_pkey(vma);
116
117 mmap_read_unlock(mm);
118
119 /*
120 * If we are in kernel mode, bail out with a SEGV, this will
121 * be caught by the assembly which will restore the non-volatile
122 * registers before calling bad_page_fault()
123 */
124 if (!user_mode(regs))
125 return SIGSEGV;
126
127 _exception_pkey(regs, address, pkey);
128
129 return 0;
130}
131
132static noinline int bad_access(struct pt_regs *regs, unsigned long address)
133{
134 return __bad_area(regs, address, SEGV_ACCERR);
135}
136
137static int do_sigbus(struct pt_regs *regs, unsigned long address,
138 vm_fault_t fault)
139{
140 if (!user_mode(regs))
141 return SIGBUS;
142
143 current->thread.trap_nr = BUS_ADRERR;
144#ifdef CONFIG_MEMORY_FAILURE
145 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
146 unsigned int lsb = 0; /* shutup gcc */
147
148 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
149 current->comm, current->pid, address);
150
151 if (fault & VM_FAULT_HWPOISON_LARGE)
152 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
153 if (fault & VM_FAULT_HWPOISON)
154 lsb = PAGE_SHIFT;
155
156 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
157 return 0;
158 }
159
160#endif
161 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
162 return 0;
163}
164
165static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
166 vm_fault_t fault)
167{
168 /*
169 * Kernel page fault interrupted by SIGKILL. We have no reason to
170 * continue processing.
171 */
172 if (fatal_signal_pending(current) && !user_mode(regs))
173 return SIGKILL;
174
175 /* Out of memory */
176 if (fault & VM_FAULT_OOM) {
177 /*
178 * We ran out of memory, or some other thing happened to us that
179 * made us unable to handle the page fault gracefully.
180 */
181 if (!user_mode(regs))
182 return SIGSEGV;
183 pagefault_out_of_memory();
184 } else {
185 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
186 VM_FAULT_HWPOISON_LARGE))
187 return do_sigbus(regs, addr, fault);
188 else if (fault & VM_FAULT_SIGSEGV)
189 return bad_area_nosemaphore(regs, addr);
190 else
191 BUG();
192 }
193 return 0;
194}
195
196/* Is this a bad kernel fault ? */
197static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
198 unsigned long address, bool is_write)
199{
200 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
201
202 if (is_exec) {
203 pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
204 address >= TASK_SIZE ? "exec-protected" : "user",
205 address,
206 from_kuid(&init_user_ns, current_uid()));
207
208 // Kernel exec fault is always bad
209 return true;
210 }
211
212 // Kernel fault on kernel address is bad
213 if (address >= TASK_SIZE)
214 return true;
215
216 // Read/write fault blocked by KUAP is bad, it can never succeed.
217 if (bad_kuap_fault(regs, address, is_write)) {
218 pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
219 is_write ? "write" : "read", address,
220 from_kuid(&init_user_ns, current_uid()));
221
222 // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
223 if (!search_exception_tables(regs->nip))
224 return true;
225
226 // Read/write fault in a valid region (the exception table search passed
227 // above), but blocked by KUAP is bad, it can never succeed.
228 return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
229 }
230
231 // What's left? Kernel fault on user and allowed by KUAP in the faulting context.
232 return false;
233}
234
235static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
236 struct vm_area_struct *vma)
237{
238 /*
239 * Make sure to check the VMA so that we do not perform
240 * faults just to hit a pkey fault as soon as we fill in a
241 * page. Only called for current mm, hence foreign == 0
242 */
243 if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
244 return true;
245
246 return false;
247}
248
249static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
250{
251 /*
252 * Allow execution from readable areas if the MMU does not
253 * provide separate controls over reading and executing.
254 *
255 * Note: That code used to not be enabled for 4xx/BookE.
256 * It is now as I/D cache coherency for these is done at
257 * set_pte_at() time and I see no reason why the test
258 * below wouldn't be valid on those processors. This -may-
259 * break programs compiled with a really old ABI though.
260 */
261 if (is_exec) {
262 return !(vma->vm_flags & VM_EXEC) &&
263 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
264 !(vma->vm_flags & (VM_READ | VM_WRITE)));
265 }
266
267 if (is_write) {
268 if (unlikely(!(vma->vm_flags & VM_WRITE)))
269 return true;
270 return false;
271 }
272
273 /*
274 * Check for a read fault. This could be caused by a read on an
275 * inaccessible page (i.e. PROT_NONE), or a Radix MMU execute-only page.
276 */
277 if (unlikely(!(vma->vm_flags & VM_READ)))
278 return true;
279 /*
280 * We should ideally do the vma pkey access check here. But in the
281 * fault path, handle_mm_fault() also does the same check. To avoid
282 * these multiple checks, we skip it here and handle access error due
283 * to pkeys later.
284 */
285 return false;
286}
287
288#ifdef CONFIG_PPC_SMLPAR
289static inline void cmo_account_page_fault(void)
290{
291 if (firmware_has_feature(FW_FEATURE_CMO)) {
292 u32 page_ins;
293
294 preempt_disable();
295 page_ins = be32_to_cpu(get_lppaca()->page_ins);
296 page_ins += 1 << PAGE_FACTOR;
297 get_lppaca()->page_ins = cpu_to_be32(page_ins);
298 preempt_enable();
299 }
300}
301#else
302static inline void cmo_account_page_fault(void) { }
303#endif /* CONFIG_PPC_SMLPAR */
304
305static void sanity_check_fault(bool is_write, bool is_user,
306 unsigned long error_code, unsigned long address)
307{
308 /*
309 * Userspace trying to access kernel address, we get PROTFAULT for that.
310 */
311 if (is_user && address >= TASK_SIZE) {
312 if ((long)address == -1)
313 return;
314
315 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
316 current->comm, current->pid, address,
317 from_kuid(&init_user_ns, current_uid()));
318 return;
319 }
320
321 if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
322 return;
323
324 /*
325 * For hash translation mode, we should never get a
326 * PROTFAULT. Any update to pte to reduce access will result in us
327 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
328 * fault instead of DSISR_PROTFAULT.
329 *
330 * A pte update to relax the access will not result in a hash page table
331 * entry invalidate and hence can result in DSISR_PROTFAULT.
332 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
333 * the special !is_write in the below conditional.
334 *
335 * For platforms that doesn't supports coherent icache and do support
336 * per page noexec bit, we do setup things such that we do the
337 * sync between D/I cache via fault. But that is handled via low level
338 * hash fault code (hash_page_do_lazy_icache()) and we should not reach
339 * here in such case.
340 *
341 * For wrong access that can result in PROTFAULT, the above vma->vm_flags
342 * check should handle those and hence we should fall to the bad_area
343 * handling correctly.
344 *
345 * For embedded with per page exec support that doesn't support coherent
346 * icache we do get PROTFAULT and we handle that D/I cache sync in
347 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
348 * is conditional for server MMU.
349 *
350 * For radix, we can get prot fault for autonuma case, because radix
351 * page table will have them marked noaccess for user.
352 */
353 if (radix_enabled() || is_write)
354 return;
355
356 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
357}
358
359/*
360 * Define the correct "is_write" bit in error_code based
361 * on the processor family
362 */
363#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
364#define page_fault_is_write(__err) ((__err) & ESR_DST)
365#else
366#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
367#endif
368
369#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
370#define page_fault_is_bad(__err) (0)
371#elif defined(CONFIG_PPC_8xx)
372#define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
373#elif defined(CONFIG_PPC64)
374static int page_fault_is_bad(unsigned long err)
375{
376 unsigned long flag = DSISR_BAD_FAULT_64S;
377
378 /*
379 * PAPR+ v2.11 § 14.15.3.4.1 (unreleased)
380 * If byte 0, bit 3 of pi-attribute-specifier-type in
381 * ibm,pi-features property is defined, ignore the DSI error
382 * which is caused by the paste instruction on the
383 * suspended NX window.
384 */
385 if (mmu_has_feature(MMU_FTR_NX_DSI))
386 flag &= ~DSISR_BAD_COPYPASTE;
387
388 return err & flag;
389}
390#else
391#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
392#endif
393
394/*
395 * For 600- and 800-family processors, the error_code parameter is DSISR
396 * for a data fault, SRR1 for an instruction fault.
397 * For 400-family processors the error_code parameter is ESR for a data fault,
398 * 0 for an instruction fault.
399 * For 64-bit processors, the error_code parameter is DSISR for a data access
400 * fault, SRR1 & 0x08000000 for an instruction access fault.
401 *
402 * The return value is 0 if the fault was handled, or the signal
403 * number if this is a kernel fault that can't be handled here.
404 */
405static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
406 unsigned long error_code)
407{
408 struct vm_area_struct * vma;
409 struct mm_struct *mm = current->mm;
410 unsigned int flags = FAULT_FLAG_DEFAULT;
411 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
412 int is_user = user_mode(regs);
413 int is_write = page_fault_is_write(error_code);
414 vm_fault_t fault, major = 0;
415 bool kprobe_fault = kprobe_page_fault(regs, 11);
416
417 if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
418 return 0;
419
420 if (unlikely(page_fault_is_bad(error_code))) {
421 if (is_user) {
422 _exception(SIGBUS, regs, BUS_OBJERR, address);
423 return 0;
424 }
425 return SIGBUS;
426 }
427
428 /* Additional sanity check(s) */
429 sanity_check_fault(is_write, is_user, error_code, address);
430
431 /*
432 * The kernel should never take an execute fault nor should it
433 * take a page fault to a kernel address or a page fault to a user
434 * address outside of dedicated places
435 */
436 if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) {
437 if (kfence_handle_page_fault(address, is_write, regs))
438 return 0;
439
440 return SIGSEGV;
441 }
442
443 /*
444 * If we're in an interrupt, have no user context or are running
445 * in a region with pagefaults disabled then we must not take the fault
446 */
447 if (unlikely(faulthandler_disabled() || !mm)) {
448 if (is_user)
449 printk_ratelimited(KERN_ERR "Page fault in user mode"
450 " with faulthandler_disabled()=%d"
451 " mm=%p\n",
452 faulthandler_disabled(), mm);
453 return bad_area_nosemaphore(regs, address);
454 }
455
456 interrupt_cond_local_irq_enable(regs);
457
458 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
459
460 /*
461 * We want to do this outside mmap_lock, because reading code around nip
462 * can result in fault, which will cause a deadlock when called with
463 * mmap_lock held
464 */
465 if (is_user)
466 flags |= FAULT_FLAG_USER;
467 if (is_write)
468 flags |= FAULT_FLAG_WRITE;
469 if (is_exec)
470 flags |= FAULT_FLAG_INSTRUCTION;
471
472 /* When running in the kernel we expect faults to occur only to
473 * addresses in user space. All other faults represent errors in the
474 * kernel and should generate an OOPS. Unfortunately, in the case of an
475 * erroneous fault occurring in a code path which already holds mmap_lock
476 * we will deadlock attempting to validate the fault against the
477 * address space. Luckily the kernel only validly references user
478 * space from well defined areas of code, which are listed in the
479 * exceptions table.
480 *
481 * As the vast majority of faults will be valid we will only perform
482 * the source reference check when there is a possibility of a deadlock.
483 * Attempt to lock the address space, if we cannot we then validate the
484 * source. If this is invalid we can skip the address space check,
485 * thus avoiding the deadlock.
486 */
487 if (unlikely(!mmap_read_trylock(mm))) {
488 if (!is_user && !search_exception_tables(regs->nip))
489 return bad_area_nosemaphore(regs, address);
490
491retry:
492 mmap_read_lock(mm);
493 } else {
494 /*
495 * The above down_read_trylock() might have succeeded in
496 * which case we'll have missed the might_sleep() from
497 * down_read():
498 */
499 might_sleep();
500 }
501
502 vma = find_vma(mm, address);
503 if (unlikely(!vma))
504 return bad_area(regs, address);
505
506 if (unlikely(vma->vm_start > address)) {
507 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
508 return bad_area(regs, address);
509
510 if (unlikely(expand_stack(vma, address)))
511 return bad_area(regs, address);
512 }
513
514 if (unlikely(access_pkey_error(is_write, is_exec,
515 (error_code & DSISR_KEYFAULT), vma)))
516 return bad_access_pkey(regs, address, vma);
517
518 if (unlikely(access_error(is_write, is_exec, vma)))
519 return bad_access(regs, address);
520
521 /*
522 * If for any reason at all we couldn't handle the fault,
523 * make sure we exit gracefully rather than endlessly redo
524 * the fault.
525 */
526 fault = handle_mm_fault(vma, address, flags, regs);
527
528 major |= fault & VM_FAULT_MAJOR;
529
530 if (fault_signal_pending(fault, regs))
531 return user_mode(regs) ? 0 : SIGBUS;
532
533 /* The fault is fully completed (including releasing mmap lock) */
534 if (fault & VM_FAULT_COMPLETED)
535 goto out;
536
537 /*
538 * Handle the retry right now, the mmap_lock has been released in that
539 * case.
540 */
541 if (unlikely(fault & VM_FAULT_RETRY)) {
542 flags |= FAULT_FLAG_TRIED;
543 goto retry;
544 }
545
546 mmap_read_unlock(current->mm);
547
548 if (unlikely(fault & VM_FAULT_ERROR))
549 return mm_fault_error(regs, address, fault);
550
551out:
552 /*
553 * Major/minor page fault accounting.
554 */
555 if (major)
556 cmo_account_page_fault();
557
558 return 0;
559}
560NOKPROBE_SYMBOL(___do_page_fault);
561
562static __always_inline void __do_page_fault(struct pt_regs *regs)
563{
564 long err;
565
566 err = ___do_page_fault(regs, regs->dar, regs->dsisr);
567 if (unlikely(err))
568 bad_page_fault(regs, err);
569}
570
571DEFINE_INTERRUPT_HANDLER(do_page_fault)
572{
573 __do_page_fault(regs);
574}
575
576#ifdef CONFIG_PPC_BOOK3S_64
577/* Same as do_page_fault but interrupt entry has already run in do_hash_fault */
578void hash__do_page_fault(struct pt_regs *regs)
579{
580 __do_page_fault(regs);
581}
582NOKPROBE_SYMBOL(hash__do_page_fault);
583#endif
584
585/*
586 * bad_page_fault is called when we have a bad access from the kernel.
587 * It is called from the DSI and ISI handlers in head.S and from some
588 * of the procedures in traps.c.
589 */
590static void __bad_page_fault(struct pt_regs *regs, int sig)
591{
592 int is_write = page_fault_is_write(regs->dsisr);
593 const char *msg;
594
595 /* kernel has accessed a bad area */
596
597 if (regs->dar < PAGE_SIZE)
598 msg = "Kernel NULL pointer dereference";
599 else
600 msg = "Unable to handle kernel data access";
601
602 switch (TRAP(regs)) {
603 case INTERRUPT_DATA_STORAGE:
604 case INTERRUPT_H_DATA_STORAGE:
605 pr_alert("BUG: %s on %s at 0x%08lx\n", msg,
606 is_write ? "write" : "read", regs->dar);
607 break;
608 case INTERRUPT_DATA_SEGMENT:
609 pr_alert("BUG: %s at 0x%08lx\n", msg, regs->dar);
610 break;
611 case INTERRUPT_INST_STORAGE:
612 case INTERRUPT_INST_SEGMENT:
613 pr_alert("BUG: Unable to handle kernel instruction fetch%s",
614 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
615 break;
616 case INTERRUPT_ALIGNMENT:
617 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
618 regs->dar);
619 break;
620 default:
621 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
622 regs->dar);
623 break;
624 }
625 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
626 regs->nip);
627
628 if (task_stack_end_corrupted(current))
629 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
630
631 die("Kernel access of bad area", regs, sig);
632}
633
634void bad_page_fault(struct pt_regs *regs, int sig)
635{
636 const struct exception_table_entry *entry;
637
638 /* Are we prepared to handle this fault? */
639 entry = search_exception_tables(instruction_pointer(regs));
640 if (entry)
641 instruction_pointer_set(regs, extable_fixup(entry));
642 else
643 __bad_page_fault(regs, sig);
644}
645
646#ifdef CONFIG_PPC_BOOK3S_64
647DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv)
648{
649 bad_page_fault(regs, SIGSEGV);
650}
651
652/*
653 * In radix, segment interrupts indicate the EA is not addressable by the
654 * page table geometry, so they are always sent here.
655 *
656 * In hash, this is called if do_slb_fault returns error. Typically it is
657 * because the EA was outside the region allowed by software.
658 */
659DEFINE_INTERRUPT_HANDLER(do_bad_segment_interrupt)
660{
661 int err = regs->result;
662
663 if (err == -EFAULT) {
664 if (user_mode(regs))
665 _exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar);
666 else
667 bad_page_fault(regs, SIGSEGV);
668 } else if (err == -EINVAL) {
669 unrecoverable_exception(regs);
670 } else {
671 BUG();
672 }
673}
674#endif
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PowerPC version
4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
5 *
6 * Derived from "arch/i386/mm/fault.c"
7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 *
9 * Modified by Cort Dougan and Paul Mackerras.
10 *
11 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
12 */
13
14#include <linux/signal.h>
15#include <linux/sched.h>
16#include <linux/sched/task_stack.h>
17#include <linux/kernel.h>
18#include <linux/errno.h>
19#include <linux/string.h>
20#include <linux/types.h>
21#include <linux/pagemap.h>
22#include <linux/ptrace.h>
23#include <linux/mman.h>
24#include <linux/mm.h>
25#include <linux/interrupt.h>
26#include <linux/highmem.h>
27#include <linux/extable.h>
28#include <linux/kprobes.h>
29#include <linux/kdebug.h>
30#include <linux/perf_event.h>
31#include <linux/ratelimit.h>
32#include <linux/context_tracking.h>
33#include <linux/hugetlb.h>
34#include <linux/uaccess.h>
35#include <linux/kfence.h>
36#include <linux/pkeys.h>
37
38#include <asm/firmware.h>
39#include <asm/interrupt.h>
40#include <asm/page.h>
41#include <asm/mmu.h>
42#include <asm/mmu_context.h>
43#include <asm/siginfo.h>
44#include <asm/debug.h>
45#include <asm/kup.h>
46#include <asm/inst.h>
47
48
49/*
50 * do_page_fault error handling helpers
51 */
52
53static int
54__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
55{
56 /*
57 * If we are in kernel mode, bail out with a SEGV, this will
58 * be caught by the assembly which will restore the non-volatile
59 * registers before calling bad_page_fault()
60 */
61 if (!user_mode(regs))
62 return SIGSEGV;
63
64 _exception(SIGSEGV, regs, si_code, address);
65
66 return 0;
67}
68
69static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
70{
71 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
72}
73
74static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
75{
76 struct mm_struct *mm = current->mm;
77
78 /*
79 * Something tried to access memory that isn't in our memory map..
80 * Fix it, but check if it's kernel or user first..
81 */
82 mmap_read_unlock(mm);
83
84 return __bad_area_nosemaphore(regs, address, si_code);
85}
86
87static noinline int bad_area(struct pt_regs *regs, unsigned long address)
88{
89 return __bad_area(regs, address, SEGV_MAPERR);
90}
91
92static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
93 struct vm_area_struct *vma)
94{
95 struct mm_struct *mm = current->mm;
96 int pkey;
97
98 /*
99 * We don't try to fetch the pkey from page table because reading
100 * page table without locking doesn't guarantee stable pte value.
101 * Hence the pkey value that we return to userspace can be different
102 * from the pkey that actually caused access error.
103 *
104 * It does *not* guarantee that the VMA we find here
105 * was the one that we faulted on.
106 *
107 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
108 * 2. T1 : set AMR to deny access to pkey=4, touches, page
109 * 3. T1 : faults...
110 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
111 * 5. T1 : enters fault handler, takes mmap_lock, etc...
112 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
113 * faulted on a pte with its pkey=4.
114 */
115 pkey = vma_pkey(vma);
116
117 mmap_read_unlock(mm);
118
119 /*
120 * If we are in kernel mode, bail out with a SEGV, this will
121 * be caught by the assembly which will restore the non-volatile
122 * registers before calling bad_page_fault()
123 */
124 if (!user_mode(regs))
125 return SIGSEGV;
126
127 _exception_pkey(regs, address, pkey);
128
129 return 0;
130}
131
132static noinline int bad_access(struct pt_regs *regs, unsigned long address)
133{
134 return __bad_area(regs, address, SEGV_ACCERR);
135}
136
137static int do_sigbus(struct pt_regs *regs, unsigned long address,
138 vm_fault_t fault)
139{
140 if (!user_mode(regs))
141 return SIGBUS;
142
143 current->thread.trap_nr = BUS_ADRERR;
144#ifdef CONFIG_MEMORY_FAILURE
145 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
146 unsigned int lsb = 0; /* shutup gcc */
147
148 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
149 current->comm, current->pid, address);
150
151 if (fault & VM_FAULT_HWPOISON_LARGE)
152 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
153 if (fault & VM_FAULT_HWPOISON)
154 lsb = PAGE_SHIFT;
155
156 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
157 return 0;
158 }
159
160#endif
161 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
162 return 0;
163}
164
165static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
166 vm_fault_t fault)
167{
168 /*
169 * Kernel page fault interrupted by SIGKILL. We have no reason to
170 * continue processing.
171 */
172 if (fatal_signal_pending(current) && !user_mode(regs))
173 return SIGKILL;
174
175 /* Out of memory */
176 if (fault & VM_FAULT_OOM) {
177 /*
178 * We ran out of memory, or some other thing happened to us that
179 * made us unable to handle the page fault gracefully.
180 */
181 if (!user_mode(regs))
182 return SIGSEGV;
183 pagefault_out_of_memory();
184 } else {
185 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
186 VM_FAULT_HWPOISON_LARGE))
187 return do_sigbus(regs, addr, fault);
188 else if (fault & VM_FAULT_SIGSEGV)
189 return bad_area_nosemaphore(regs, addr);
190 else
191 BUG();
192 }
193 return 0;
194}
195
196/* Is this a bad kernel fault ? */
197static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
198 unsigned long address, bool is_write)
199{
200 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
201
202 if (is_exec) {
203 pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
204 address >= TASK_SIZE ? "exec-protected" : "user",
205 address,
206 from_kuid(&init_user_ns, current_uid()));
207
208 // Kernel exec fault is always bad
209 return true;
210 }
211
212 // Kernel fault on kernel address is bad
213 if (address >= TASK_SIZE)
214 return true;
215
216 // Read/write fault blocked by KUAP is bad, it can never succeed.
217 if (bad_kuap_fault(regs, address, is_write)) {
218 pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
219 is_write ? "write" : "read", address,
220 from_kuid(&init_user_ns, current_uid()));
221
222 // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
223 if (!search_exception_tables(regs->nip))
224 return true;
225
226 // Read/write fault in a valid region (the exception table search passed
227 // above), but blocked by KUAP is bad, it can never succeed.
228 return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
229 }
230
231 // What's left? Kernel fault on user and allowed by KUAP in the faulting context.
232 return false;
233}
234
235static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
236 struct vm_area_struct *vma)
237{
238 /*
239 * Make sure to check the VMA so that we do not perform
240 * faults just to hit a pkey fault as soon as we fill in a
241 * page. Only called for current mm, hence foreign == 0
242 */
243 if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
244 return true;
245
246 return false;
247}
248
249static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
250{
251 /*
252 * Allow execution from readable areas if the MMU does not
253 * provide separate controls over reading and executing.
254 *
255 * Note: That code used to not be enabled for 4xx/BookE.
256 * It is now as I/D cache coherency for these is done at
257 * set_pte_at() time and I see no reason why the test
258 * below wouldn't be valid on those processors. This -may-
259 * break programs compiled with a really old ABI though.
260 */
261 if (is_exec) {
262 return !(vma->vm_flags & VM_EXEC) &&
263 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
264 !(vma->vm_flags & (VM_READ | VM_WRITE)));
265 }
266
267 if (is_write) {
268 if (unlikely(!(vma->vm_flags & VM_WRITE)))
269 return true;
270 return false;
271 }
272
273 if (unlikely(!vma_is_accessible(vma)))
274 return true;
275 /*
276 * We should ideally do the vma pkey access check here. But in the
277 * fault path, handle_mm_fault() also does the same check. To avoid
278 * these multiple checks, we skip it here and handle access error due
279 * to pkeys later.
280 */
281 return false;
282}
283
284#ifdef CONFIG_PPC_SMLPAR
285static inline void cmo_account_page_fault(void)
286{
287 if (firmware_has_feature(FW_FEATURE_CMO)) {
288 u32 page_ins;
289
290 preempt_disable();
291 page_ins = be32_to_cpu(get_lppaca()->page_ins);
292 page_ins += 1 << PAGE_FACTOR;
293 get_lppaca()->page_ins = cpu_to_be32(page_ins);
294 preempt_enable();
295 }
296}
297#else
298static inline void cmo_account_page_fault(void) { }
299#endif /* CONFIG_PPC_SMLPAR */
300
301static void sanity_check_fault(bool is_write, bool is_user,
302 unsigned long error_code, unsigned long address)
303{
304 /*
305 * Userspace trying to access kernel address, we get PROTFAULT for that.
306 */
307 if (is_user && address >= TASK_SIZE) {
308 if ((long)address == -1)
309 return;
310
311 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
312 current->comm, current->pid, address,
313 from_kuid(&init_user_ns, current_uid()));
314 return;
315 }
316
317 if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
318 return;
319
320 /*
321 * For hash translation mode, we should never get a
322 * PROTFAULT. Any update to pte to reduce access will result in us
323 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
324 * fault instead of DSISR_PROTFAULT.
325 *
326 * A pte update to relax the access will not result in a hash page table
327 * entry invalidate and hence can result in DSISR_PROTFAULT.
328 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
329 * the special !is_write in the below conditional.
330 *
331 * For platforms that doesn't supports coherent icache and do support
332 * per page noexec bit, we do setup things such that we do the
333 * sync between D/I cache via fault. But that is handled via low level
334 * hash fault code (hash_page_do_lazy_icache()) and we should not reach
335 * here in such case.
336 *
337 * For wrong access that can result in PROTFAULT, the above vma->vm_flags
338 * check should handle those and hence we should fall to the bad_area
339 * handling correctly.
340 *
341 * For embedded with per page exec support that doesn't support coherent
342 * icache we do get PROTFAULT and we handle that D/I cache sync in
343 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
344 * is conditional for server MMU.
345 *
346 * For radix, we can get prot fault for autonuma case, because radix
347 * page table will have them marked noaccess for user.
348 */
349 if (radix_enabled() || is_write)
350 return;
351
352 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
353}
354
355/*
356 * Define the correct "is_write" bit in error_code based
357 * on the processor family
358 */
359#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
360#define page_fault_is_write(__err) ((__err) & ESR_DST)
361#else
362#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
363#endif
364
365#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
366#define page_fault_is_bad(__err) (0)
367#elif defined(CONFIG_PPC_8xx)
368#define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
369#elif defined(CONFIG_PPC64)
370#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
371#else
372#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
373#endif
374
375/*
376 * For 600- and 800-family processors, the error_code parameter is DSISR
377 * for a data fault, SRR1 for an instruction fault.
378 * For 400-family processors the error_code parameter is ESR for a data fault,
379 * 0 for an instruction fault.
380 * For 64-bit processors, the error_code parameter is DSISR for a data access
381 * fault, SRR1 & 0x08000000 for an instruction access fault.
382 *
383 * The return value is 0 if the fault was handled, or the signal
384 * number if this is a kernel fault that can't be handled here.
385 */
386static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
387 unsigned long error_code)
388{
389 struct vm_area_struct * vma;
390 struct mm_struct *mm = current->mm;
391 unsigned int flags = FAULT_FLAG_DEFAULT;
392 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
393 int is_user = user_mode(regs);
394 int is_write = page_fault_is_write(error_code);
395 vm_fault_t fault, major = 0;
396 bool kprobe_fault = kprobe_page_fault(regs, 11);
397
398 if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
399 return 0;
400
401 if (unlikely(page_fault_is_bad(error_code))) {
402 if (is_user) {
403 _exception(SIGBUS, regs, BUS_OBJERR, address);
404 return 0;
405 }
406 return SIGBUS;
407 }
408
409 /* Additional sanity check(s) */
410 sanity_check_fault(is_write, is_user, error_code, address);
411
412 /*
413 * The kernel should never take an execute fault nor should it
414 * take a page fault to a kernel address or a page fault to a user
415 * address outside of dedicated places
416 */
417 if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) {
418 if (kfence_handle_page_fault(address, is_write, regs))
419 return 0;
420
421 return SIGSEGV;
422 }
423
424 /*
425 * If we're in an interrupt, have no user context or are running
426 * in a region with pagefaults disabled then we must not take the fault
427 */
428 if (unlikely(faulthandler_disabled() || !mm)) {
429 if (is_user)
430 printk_ratelimited(KERN_ERR "Page fault in user mode"
431 " with faulthandler_disabled()=%d"
432 " mm=%p\n",
433 faulthandler_disabled(), mm);
434 return bad_area_nosemaphore(regs, address);
435 }
436
437 interrupt_cond_local_irq_enable(regs);
438
439 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
440
441 /*
442 * We want to do this outside mmap_lock, because reading code around nip
443 * can result in fault, which will cause a deadlock when called with
444 * mmap_lock held
445 */
446 if (is_user)
447 flags |= FAULT_FLAG_USER;
448 if (is_write)
449 flags |= FAULT_FLAG_WRITE;
450 if (is_exec)
451 flags |= FAULT_FLAG_INSTRUCTION;
452
453 /* When running in the kernel we expect faults to occur only to
454 * addresses in user space. All other faults represent errors in the
455 * kernel and should generate an OOPS. Unfortunately, in the case of an
456 * erroneous fault occurring in a code path which already holds mmap_lock
457 * we will deadlock attempting to validate the fault against the
458 * address space. Luckily the kernel only validly references user
459 * space from well defined areas of code, which are listed in the
460 * exceptions table.
461 *
462 * As the vast majority of faults will be valid we will only perform
463 * the source reference check when there is a possibility of a deadlock.
464 * Attempt to lock the address space, if we cannot we then validate the
465 * source. If this is invalid we can skip the address space check,
466 * thus avoiding the deadlock.
467 */
468 if (unlikely(!mmap_read_trylock(mm))) {
469 if (!is_user && !search_exception_tables(regs->nip))
470 return bad_area_nosemaphore(regs, address);
471
472retry:
473 mmap_read_lock(mm);
474 } else {
475 /*
476 * The above down_read_trylock() might have succeeded in
477 * which case we'll have missed the might_sleep() from
478 * down_read():
479 */
480 might_sleep();
481 }
482
483 vma = find_vma(mm, address);
484 if (unlikely(!vma))
485 return bad_area(regs, address);
486
487 if (unlikely(vma->vm_start > address)) {
488 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
489 return bad_area(regs, address);
490
491 if (unlikely(expand_stack(vma, address)))
492 return bad_area(regs, address);
493 }
494
495 if (unlikely(access_pkey_error(is_write, is_exec,
496 (error_code & DSISR_KEYFAULT), vma)))
497 return bad_access_pkey(regs, address, vma);
498
499 if (unlikely(access_error(is_write, is_exec, vma)))
500 return bad_access(regs, address);
501
502 /*
503 * If for any reason at all we couldn't handle the fault,
504 * make sure we exit gracefully rather than endlessly redo
505 * the fault.
506 */
507 fault = handle_mm_fault(vma, address, flags, regs);
508
509 major |= fault & VM_FAULT_MAJOR;
510
511 if (fault_signal_pending(fault, regs))
512 return user_mode(regs) ? 0 : SIGBUS;
513
514 /*
515 * Handle the retry right now, the mmap_lock has been released in that
516 * case.
517 */
518 if (unlikely(fault & VM_FAULT_RETRY)) {
519 if (flags & FAULT_FLAG_ALLOW_RETRY) {
520 flags |= FAULT_FLAG_TRIED;
521 goto retry;
522 }
523 }
524
525 mmap_read_unlock(current->mm);
526
527 if (unlikely(fault & VM_FAULT_ERROR))
528 return mm_fault_error(regs, address, fault);
529
530 /*
531 * Major/minor page fault accounting.
532 */
533 if (major)
534 cmo_account_page_fault();
535
536 return 0;
537}
538NOKPROBE_SYMBOL(___do_page_fault);
539
540static __always_inline void __do_page_fault(struct pt_regs *regs)
541{
542 long err;
543
544 err = ___do_page_fault(regs, regs->dar, regs->dsisr);
545 if (unlikely(err))
546 bad_page_fault(regs, err);
547}
548
549DEFINE_INTERRUPT_HANDLER(do_page_fault)
550{
551 __do_page_fault(regs);
552}
553
554#ifdef CONFIG_PPC_BOOK3S_64
555/* Same as do_page_fault but interrupt entry has already run in do_hash_fault */
556void hash__do_page_fault(struct pt_regs *regs)
557{
558 __do_page_fault(regs);
559}
560NOKPROBE_SYMBOL(hash__do_page_fault);
561#endif
562
563/*
564 * bad_page_fault is called when we have a bad access from the kernel.
565 * It is called from the DSI and ISI handlers in head.S and from some
566 * of the procedures in traps.c.
567 */
568static void __bad_page_fault(struct pt_regs *regs, int sig)
569{
570 int is_write = page_fault_is_write(regs->dsisr);
571
572 /* kernel has accessed a bad area */
573
574 switch (TRAP(regs)) {
575 case INTERRUPT_DATA_STORAGE:
576 case INTERRUPT_DATA_SEGMENT:
577 case INTERRUPT_H_DATA_STORAGE:
578 pr_alert("BUG: %s on %s at 0x%08lx\n",
579 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
580 "Unable to handle kernel data access",
581 is_write ? "write" : "read", regs->dar);
582 break;
583 case INTERRUPT_INST_STORAGE:
584 case INTERRUPT_INST_SEGMENT:
585 pr_alert("BUG: Unable to handle kernel instruction fetch%s",
586 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
587 break;
588 case INTERRUPT_ALIGNMENT:
589 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
590 regs->dar);
591 break;
592 default:
593 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
594 regs->dar);
595 break;
596 }
597 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
598 regs->nip);
599
600 if (task_stack_end_corrupted(current))
601 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
602
603 die("Kernel access of bad area", regs, sig);
604}
605
606void bad_page_fault(struct pt_regs *regs, int sig)
607{
608 const struct exception_table_entry *entry;
609
610 /* Are we prepared to handle this fault? */
611 entry = search_exception_tables(instruction_pointer(regs));
612 if (entry)
613 instruction_pointer_set(regs, extable_fixup(entry));
614 else
615 __bad_page_fault(regs, sig);
616}
617
618#ifdef CONFIG_PPC_BOOK3S_64
619DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv)
620{
621 bad_page_fault(regs, SIGSEGV);
622}
623#endif