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1// SPDX-License-Identifier: GPL-2.02/*3 * This file contains common KASAN error reporting code.4 *5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>7 *8 * Some code borrowed from https://github.com/xairy/kasan-prototype by9 * Andrey Konovalov <andreyknvl@gmail.com>10 */11 12#include <kunit/test.h>13#include <linux/bitops.h>14#include <linux/ftrace.h>15#include <linux/init.h>16#include <linux/kernel.h>17#include <linux/lockdep.h>18#include <linux/mm.h>19#include <linux/printk.h>20#include <linux/sched.h>21#include <linux/slab.h>22#include <linux/stackdepot.h>23#include <linux/stacktrace.h>24#include <linux/string.h>25#include <linux/types.h>26#include <linux/vmalloc.h>27#include <linux/kasan.h>28#include <linux/module.h>29#include <linux/sched/task_stack.h>30#include <linux/uaccess.h>31#include <trace/events/error_report.h>32 33#include <asm/sections.h>34 35#include "kasan.h"36#include "../slab.h"37 38static unsigned long kasan_flags;39 40#define KASAN_BIT_REPORTED 041#define KASAN_BIT_MULTI_SHOT 142 43enum kasan_arg_fault {44 KASAN_ARG_FAULT_DEFAULT,45 KASAN_ARG_FAULT_REPORT,46 KASAN_ARG_FAULT_PANIC,47 KASAN_ARG_FAULT_PANIC_ON_WRITE,48};49 50static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;51 52/* kasan.fault=report/panic */53static int __init early_kasan_fault(char *arg)54{55 if (!arg)56 return -EINVAL;57 58 if (!strcmp(arg, "report"))59 kasan_arg_fault = KASAN_ARG_FAULT_REPORT;60 else if (!strcmp(arg, "panic"))61 kasan_arg_fault = KASAN_ARG_FAULT_PANIC;62 else if (!strcmp(arg, "panic_on_write"))63 kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE;64 else65 return -EINVAL;66 67 return 0;68}69early_param("kasan.fault", early_kasan_fault);70 71static int __init kasan_set_multi_shot(char *str)72{73 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);74 return 1;75}76__setup("kasan_multi_shot", kasan_set_multi_shot);77 78/*79 * This function is used to check whether KASAN reports are suppressed for80 * software KASAN modes via kasan_disable/enable_current() critical sections.81 *82 * This is done to avoid:83 * 1. False-positive reports when accessing slab metadata,84 * 2. Deadlocking when poisoned memory is accessed by the reporting code.85 *86 * Hardware Tag-Based KASAN instead relies on:87 * For #1: Resetting tags via kasan_reset_tag().88 * For #2: Suppression of tag checks via CPU, see report_suppress_start/end().89 */90static bool report_suppressed_sw(void)91{92#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)93 if (current->kasan_depth)94 return true;95#endif96 return false;97}98 99static void report_suppress_start(void)100{101#ifdef CONFIG_KASAN_HW_TAGS102 /*103 * Disable preemption for the duration of printing a KASAN report, as104 * hw_suppress_tag_checks_start() disables checks on the current CPU.105 */106 preempt_disable();107 hw_suppress_tag_checks_start();108#else109 kasan_disable_current();110#endif111}112 113static void report_suppress_stop(void)114{115#ifdef CONFIG_KASAN_HW_TAGS116 hw_suppress_tag_checks_stop();117 preempt_enable();118#else119 kasan_enable_current();120#endif121}122 123/*124 * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot125 * is enabled. Note that KASAN tests effectively enable kasan_multi_shot126 * for their duration.127 */128static bool report_enabled(void)129{130 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))131 return true;132 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);133}134 135#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)136 137bool kasan_save_enable_multi_shot(void)138{139 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);140}141EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);142 143void kasan_restore_multi_shot(bool enabled)144{145 if (!enabled)146 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);147}148EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);149 150#endif151 152#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)153 154/*155 * Whether the KASAN KUnit test suite is currently being executed.156 * Updated in kasan_test.c.157 */158static bool kasan_kunit_executing;159 160void kasan_kunit_test_suite_start(void)161{162 WRITE_ONCE(kasan_kunit_executing, true);163}164EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);165 166void kasan_kunit_test_suite_end(void)167{168 WRITE_ONCE(kasan_kunit_executing, false);169}170EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);171 172static bool kasan_kunit_test_suite_executing(void)173{174 return READ_ONCE(kasan_kunit_executing);175}176 177#else /* CONFIG_KASAN_KUNIT_TEST */178 179static inline bool kasan_kunit_test_suite_executing(void) { return false; }180 181#endif /* CONFIG_KASAN_KUNIT_TEST */182 183#if IS_ENABLED(CONFIG_KUNIT)184 185static void fail_non_kasan_kunit_test(void)186{187 struct kunit *test;188 189 if (kasan_kunit_test_suite_executing())190 return;191 192 test = current->kunit_test;193 if (test)194 kunit_set_failure(test);195}196 197#else /* CONFIG_KUNIT */198 199static inline void fail_non_kasan_kunit_test(void) { }200 201#endif /* CONFIG_KUNIT */202 203static DEFINE_SPINLOCK(report_lock);204 205static void start_report(unsigned long *flags, bool sync)206{207 fail_non_kasan_kunit_test();208 /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */209 disable_trace_on_warning();210 /* Do not allow LOCKDEP mangling KASAN reports. */211 lockdep_off();212 /* Make sure we don't end up in loop. */213 report_suppress_start();214 spin_lock_irqsave(&report_lock, *flags);215 pr_err("==================================================================\n");216}217 218static void end_report(unsigned long *flags, const void *addr, bool is_write)219{220 if (addr)221 trace_error_report_end(ERROR_DETECTOR_KASAN,222 (unsigned long)addr);223 pr_err("==================================================================\n");224 spin_unlock_irqrestore(&report_lock, *flags);225 if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))226 check_panic_on_warn("KASAN");227 switch (kasan_arg_fault) {228 case KASAN_ARG_FAULT_DEFAULT:229 case KASAN_ARG_FAULT_REPORT:230 break;231 case KASAN_ARG_FAULT_PANIC:232 panic("kasan.fault=panic set ...\n");233 break;234 case KASAN_ARG_FAULT_PANIC_ON_WRITE:235 if (is_write)236 panic("kasan.fault=panic_on_write set ...\n");237 break;238 }239 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);240 lockdep_on();241 report_suppress_stop();242}243 244static void print_error_description(struct kasan_report_info *info)245{246 pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);247 248 if (info->type != KASAN_REPORT_ACCESS) {249 pr_err("Free of addr %px by task %s/%d\n",250 info->access_addr, current->comm, task_pid_nr(current));251 return;252 }253 254 if (info->access_size)255 pr_err("%s of size %zu at addr %px by task %s/%d\n",256 info->is_write ? "Write" : "Read", info->access_size,257 info->access_addr, current->comm, task_pid_nr(current));258 else259 pr_err("%s at addr %px by task %s/%d\n",260 info->is_write ? "Write" : "Read",261 info->access_addr, current->comm, task_pid_nr(current));262}263 264static void print_track(struct kasan_track *track, const char *prefix)265{266#ifdef CONFIG_KASAN_EXTRA_INFO267 u64 ts_nsec = track->timestamp;268 unsigned long rem_usec;269 270 ts_nsec <<= 9;271 rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000;272 273 pr_err("%s by task %u on cpu %d at %lu.%06lus:\n",274 prefix, track->pid, track->cpu,275 (unsigned long)ts_nsec, rem_usec);276#else277 pr_err("%s by task %u:\n", prefix, track->pid);278#endif /* CONFIG_KASAN_EXTRA_INFO */279 if (track->stack)280 stack_depot_print(track->stack);281 else282 pr_err("(stack is not available)\n");283}284 285static inline struct page *addr_to_page(const void *addr)286{287 if (virt_addr_valid(addr))288 return virt_to_head_page(addr);289 return NULL;290}291 292static void describe_object_addr(const void *addr, struct kasan_report_info *info)293{294 unsigned long access_addr = (unsigned long)addr;295 unsigned long object_addr = (unsigned long)info->object;296 const char *rel_type, *region_state = "";297 int rel_bytes;298 299 pr_err("The buggy address belongs to the object at %px\n"300 " which belongs to the cache %s of size %d\n",301 info->object, info->cache->name, info->cache->object_size);302 303 if (access_addr < object_addr) {304 rel_type = "to the left";305 rel_bytes = object_addr - access_addr;306 } else if (access_addr >= object_addr + info->alloc_size) {307 rel_type = "to the right";308 rel_bytes = access_addr - (object_addr + info->alloc_size);309 } else {310 rel_type = "inside";311 rel_bytes = access_addr - object_addr;312 }313 314 /*315 * Tag-Based modes use the stack ring to infer the bug type, but the316 * memory region state description is generated based on the metadata.317 * Thus, defining the region state as below can contradict the metadata.318 * Fixing this requires further improvements, so only infer the state319 * for the Generic mode.320 */321 if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {322 if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)323 region_state = "allocated ";324 else if (strcmp(info->bug_type, "slab-use-after-free") == 0)325 region_state = "freed ";326 }327 328 pr_err("The buggy address is located %d bytes %s of\n"329 " %s%zu-byte region [%px, %px)\n",330 rel_bytes, rel_type, region_state, info->alloc_size,331 (void *)object_addr, (void *)(object_addr + info->alloc_size));332}333 334static void describe_object_stacks(struct kasan_report_info *info)335{336 if (info->alloc_track.stack) {337 print_track(&info->alloc_track, "Allocated");338 pr_err("\n");339 }340 341 if (info->free_track.stack) {342 print_track(&info->free_track, "Freed");343 pr_err("\n");344 }345 346 kasan_print_aux_stacks(info->cache, info->object);347}348 349static void describe_object(const void *addr, struct kasan_report_info *info)350{351 if (kasan_stack_collection_enabled())352 describe_object_stacks(info);353 describe_object_addr(addr, info);354}355 356static inline bool kernel_or_module_addr(const void *addr)357{358 if (is_kernel((unsigned long)addr))359 return true;360 if (is_module_address((unsigned long)addr))361 return true;362 return false;363}364 365static inline bool init_task_stack_addr(const void *addr)366{367 return addr >= (void *)&init_thread_union.stack &&368 (addr <= (void *)&init_thread_union.stack +369 sizeof(init_thread_union.stack));370}371 372static void print_address_description(void *addr, u8 tag,373 struct kasan_report_info *info)374{375 struct page *page = addr_to_page(addr);376 377 dump_stack_lvl(KERN_ERR);378 pr_err("\n");379 380 if (info->cache && info->object) {381 describe_object(addr, info);382 pr_err("\n");383 }384 385 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {386 pr_err("The buggy address belongs to the variable:\n");387 pr_err(" %pS\n", addr);388 pr_err("\n");389 }390 391 if (object_is_on_stack(addr)) {392 /*393 * Currently, KASAN supports printing frame information only394 * for accesses to the task's own stack.395 */396 kasan_print_address_stack_frame(addr);397 pr_err("\n");398 }399 400 if (is_vmalloc_addr(addr)) {401 struct vm_struct *va = find_vm_area(addr);402 403 if (va) {404 pr_err("The buggy address belongs to the virtual mapping at\n"405 " [%px, %px) created by:\n"406 " %pS\n",407 va->addr, va->addr + va->size, va->caller);408 pr_err("\n");409 410 page = vmalloc_to_page(addr);411 }412 }413 414 if (page) {415 pr_err("The buggy address belongs to the physical page:\n");416 dump_page(page, "kasan: bad access detected");417 pr_err("\n");418 }419}420 421static bool meta_row_is_guilty(const void *row, const void *addr)422{423 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);424}425 426static int meta_pointer_offset(const void *row, const void *addr)427{428 /*429 * Memory state around the buggy address:430 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe431 * ...432 *433 * The length of ">ff00ff00ff00ff00: " is434 * 3 + (BITS_PER_LONG / 8) * 2 chars.435 * The length of each granule metadata is 2 bytes436 * plus 1 byte for space.437 */438 return 3 + (BITS_PER_LONG / 8) * 2 +439 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;440}441 442static void print_memory_metadata(const void *addr)443{444 int i;445 void *row;446 447 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)448 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;449 450 pr_err("Memory state around the buggy address:\n");451 452 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {453 char buffer[4 + (BITS_PER_LONG / 8) * 2];454 char metadata[META_BYTES_PER_ROW];455 456 snprintf(buffer, sizeof(buffer),457 (i == 0) ? ">%px: " : " %px: ", row);458 459 /*460 * We should not pass a shadow pointer to generic461 * function, because generic functions may try to462 * access kasan mapping for the passed address.463 */464 kasan_metadata_fetch_row(&metadata[0], row);465 466 print_hex_dump(KERN_ERR, buffer,467 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,468 metadata, META_BYTES_PER_ROW, 0);469 470 if (meta_row_is_guilty(row, addr))471 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');472 473 row += META_MEM_BYTES_PER_ROW;474 }475}476 477static void print_report(struct kasan_report_info *info)478{479 void *addr = kasan_reset_tag((void *)info->access_addr);480 u8 tag = get_tag((void *)info->access_addr);481 482 print_error_description(info);483 if (addr_has_metadata(addr))484 kasan_print_tags(tag, info->first_bad_addr);485 pr_err("\n");486 487 if (addr_has_metadata(addr)) {488 print_address_description(addr, tag, info);489 print_memory_metadata(info->first_bad_addr);490 } else {491 dump_stack_lvl(KERN_ERR);492 }493}494 495static void complete_report_info(struct kasan_report_info *info)496{497 void *addr = kasan_reset_tag((void *)info->access_addr);498 struct slab *slab;499 500 if (info->type == KASAN_REPORT_ACCESS)501 info->first_bad_addr = kasan_find_first_bad_addr(502 (void *)info->access_addr, info->access_size);503 else504 info->first_bad_addr = addr;505 506 slab = kasan_addr_to_slab(addr);507 if (slab) {508 info->cache = slab->slab_cache;509 info->object = nearest_obj(info->cache, slab, addr);510 511 /* Try to determine allocation size based on the metadata. */512 info->alloc_size = kasan_get_alloc_size(info->object, info->cache);513 /* Fallback to the object size if failed. */514 if (!info->alloc_size)515 info->alloc_size = info->cache->object_size;516 } else517 info->cache = info->object = NULL;518 519 switch (info->type) {520 case KASAN_REPORT_INVALID_FREE:521 info->bug_type = "invalid-free";522 break;523 case KASAN_REPORT_DOUBLE_FREE:524 info->bug_type = "double-free";525 break;526 default:527 /* bug_type filled in by kasan_complete_mode_report_info. */528 break;529 }530 531 /* Fill in mode-specific report info fields. */532 kasan_complete_mode_report_info(info);533}534 535void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)536{537 unsigned long flags;538 struct kasan_report_info info;539 540 /*541 * Do not check report_suppressed_sw(), as an invalid-free cannot be542 * caused by accessing poisoned memory and thus should not be suppressed543 * by kasan_disable/enable_current() critical sections.544 *545 * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free()546 * is triggered by explicit tag checks and not by the ones performed by547 * the CPU. Thus, reporting invalid-free is not suppressed as well.548 */549 if (unlikely(!report_enabled()))550 return;551 552 start_report(&flags, true);553 554 __memset(&info, 0, sizeof(info));555 info.type = type;556 info.access_addr = ptr;557 info.access_size = 0;558 info.is_write = false;559 info.ip = ip;560 561 complete_report_info(&info);562 563 print_report(&info);564 565 /*566 * Invalid free is considered a "write" since the allocator's metadata567 * updates involves writes.568 */569 end_report(&flags, ptr, true);570}571 572/*573 * kasan_report() is the only reporting function that uses574 * user_access_save/restore(): kasan_report_invalid_free() cannot be called575 * from a UACCESS region, and kasan_report_async() is not used on x86.576 */577bool kasan_report(const void *addr, size_t size, bool is_write,578 unsigned long ip)579{580 bool ret = true;581 unsigned long ua_flags = user_access_save();582 unsigned long irq_flags;583 struct kasan_report_info info;584 585 if (unlikely(report_suppressed_sw()) || unlikely(!report_enabled())) {586 ret = false;587 goto out;588 }589 590 start_report(&irq_flags, true);591 592 __memset(&info, 0, sizeof(info));593 info.type = KASAN_REPORT_ACCESS;594 info.access_addr = addr;595 info.access_size = size;596 info.is_write = is_write;597 info.ip = ip;598 599 complete_report_info(&info);600 601 print_report(&info);602 603 end_report(&irq_flags, (void *)addr, is_write);604 605out:606 user_access_restore(ua_flags);607 608 return ret;609}610 611#ifdef CONFIG_KASAN_HW_TAGS612void kasan_report_async(void)613{614 unsigned long flags;615 616 /*617 * Do not check report_suppressed_sw(), as618 * kasan_disable/enable_current() critical sections do not affect619 * Hardware Tag-Based KASAN.620 */621 if (unlikely(!report_enabled()))622 return;623 624 start_report(&flags, false);625 pr_err("BUG: KASAN: invalid-access\n");626 pr_err("Asynchronous fault: no details available\n");627 pr_err("\n");628 dump_stack_lvl(KERN_ERR);629 /*630 * Conservatively set is_write=true, because no details are available.631 * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.632 */633 end_report(&flags, NULL, true);634}635#endif /* CONFIG_KASAN_HW_TAGS */636 637#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)638/*639 * With compiler-based KASAN modes, accesses to bogus pointers (outside of the640 * mapped kernel address space regions) cause faults when KASAN tries to check641 * the shadow memory before the actual memory access. This results in cryptic642 * GPF reports, which are hard for users to interpret. This hook helps users to643 * figure out what the original bogus pointer was.644 */645void kasan_non_canonical_hook(unsigned long addr)646{647 unsigned long orig_addr;648 const char *bug_type;649 650 /*651 * All addresses that came as a result of the memory-to-shadow mapping652 * (even for bogus pointers) must be >= KASAN_SHADOW_OFFSET.653 */654 if (addr < KASAN_SHADOW_OFFSET)655 return;656 657 orig_addr = (unsigned long)kasan_shadow_to_mem((void *)addr);658 659 /*660 * For faults near the shadow address for NULL, we can be fairly certain661 * that this is a KASAN shadow memory access.662 * For faults that correspond to the shadow for low or high canonical663 * addresses, we can still be pretty sure: these shadow regions are a664 * fairly narrow chunk of the address space.665 * But the shadow for non-canonical addresses is a really large chunk666 * of the address space. For this case, we still print the decoded667 * address, but make it clear that this is not necessarily what's668 * actually going on.669 */670 if (orig_addr < PAGE_SIZE)671 bug_type = "null-ptr-deref";672 else if (orig_addr < TASK_SIZE)673 bug_type = "probably user-memory-access";674 else if (addr_in_shadow((void *)addr))675 bug_type = "probably wild-memory-access";676 else677 bug_type = "maybe wild-memory-access";678 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,679 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);680}681#endif682