diff options
Diffstat (limited to 'mm/kasan/report.c')
| -rw-r--r-- | mm/kasan/report.c | 662 |
1 files changed, 662 insertions, 0 deletions
diff --git a/mm/kasan/report.c b/mm/kasan/report.c new file mode 100644 index 000000000..6e3cb118d --- /dev/null +++ b/mm/kasan/report.c @@ -0,0 +1,662 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This file contains common KASAN error reporting code. + * + * Copyright (c) 2014 Samsung Electronics Co., Ltd. + * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> + * + * Some code borrowed from https://github.com/xairy/kasan-prototype by + * Andrey Konovalov <andreyknvl@gmail.com> + */ + +#include <kunit/test.h> +#include <linux/bitops.h> +#include <linux/ftrace.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/lockdep.h> +#include <linux/mm.h> +#include <linux/printk.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/stackdepot.h> +#include <linux/stacktrace.h> +#include <linux/string.h> +#include <linux/types.h> +#include <linux/kasan.h> +#include <linux/module.h> +#include <linux/sched/task_stack.h> +#include <linux/uaccess.h> +#include <trace/events/error_report.h> + +#include <asm/sections.h> + +#include "kasan.h" +#include "../slab.h" + +static unsigned long kasan_flags; + +#define KASAN_BIT_REPORTED 0 +#define KASAN_BIT_MULTI_SHOT 1 + +enum kasan_arg_fault { + KASAN_ARG_FAULT_DEFAULT, + KASAN_ARG_FAULT_REPORT, + KASAN_ARG_FAULT_PANIC, + KASAN_ARG_FAULT_PANIC_ON_WRITE, +}; + +static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT; + +/* kasan.fault=report/panic */ +static int __init early_kasan_fault(char *arg) +{ + if (!arg) + return -EINVAL; + + if (!strcmp(arg, "report")) + kasan_arg_fault = KASAN_ARG_FAULT_REPORT; + else if (!strcmp(arg, "panic")) + kasan_arg_fault = KASAN_ARG_FAULT_PANIC; + else if (!strcmp(arg, "panic_on_write")) + kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE; + else + return -EINVAL; + + return 0; +} +early_param("kasan.fault", early_kasan_fault); + +static int __init kasan_set_multi_shot(char *str) +{ + set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); + return 1; +} +__setup("kasan_multi_shot", kasan_set_multi_shot); + +/* + * This function is used to check whether KASAN reports are suppressed for + * software KASAN modes via kasan_disable/enable_current() critical sections. + * + * This is done to avoid: + * 1. False-positive reports when accessing slab metadata, + * 2. Deadlocking when poisoned memory is accessed by the reporting code. + * + * Hardware Tag-Based KASAN instead relies on: + * For #1: Resetting tags via kasan_reset_tag(). + * For #2: Suppression of tag checks via CPU, see report_suppress_start/end(). + */ +static bool report_suppressed_sw(void) +{ +#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) + if (current->kasan_depth) + return true; +#endif + return false; +} + +static void report_suppress_start(void) +{ +#ifdef CONFIG_KASAN_HW_TAGS + /* + * Disable preemption for the duration of printing a KASAN report, as + * hw_suppress_tag_checks_start() disables checks on the current CPU. + */ + preempt_disable(); + hw_suppress_tag_checks_start(); +#else + kasan_disable_current(); +#endif +} + +static void report_suppress_stop(void) +{ +#ifdef CONFIG_KASAN_HW_TAGS + hw_suppress_tag_checks_stop(); + preempt_enable(); +#else + kasan_enable_current(); +#endif +} + +/* + * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot + * is enabled. Note that KASAN tests effectively enable kasan_multi_shot + * for their duration. + */ +static bool report_enabled(void) +{ + if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) + return true; + return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); +} + +#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST) + +bool kasan_save_enable_multi_shot(void) +{ + return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); +} +EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); + +void kasan_restore_multi_shot(bool enabled) +{ + if (!enabled) + clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); +} +EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); + +#endif + +#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) + +/* + * Whether the KASAN KUnit test suite is currently being executed. + * Updated in kasan_test.c. + */ +static bool kasan_kunit_executing; + +void kasan_kunit_test_suite_start(void) +{ + WRITE_ONCE(kasan_kunit_executing, true); +} +EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start); + +void kasan_kunit_test_suite_end(void) +{ + WRITE_ONCE(kasan_kunit_executing, false); +} +EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end); + +static bool kasan_kunit_test_suite_executing(void) +{ + return READ_ONCE(kasan_kunit_executing); +} + +#else /* CONFIG_KASAN_KUNIT_TEST */ + +static inline bool kasan_kunit_test_suite_executing(void) { return false; } + +#endif /* CONFIG_KASAN_KUNIT_TEST */ + +#if IS_ENABLED(CONFIG_KUNIT) + +static void fail_non_kasan_kunit_test(void) +{ + struct kunit *test; + + if (kasan_kunit_test_suite_executing()) + return; + + test = current->kunit_test; + if (test) + kunit_set_failure(test); +} + +#else /* CONFIG_KUNIT */ + +static inline void fail_non_kasan_kunit_test(void) { } + +#endif /* CONFIG_KUNIT */ + +static DEFINE_SPINLOCK(report_lock); + +static void start_report(unsigned long *flags, bool sync) +{ + fail_non_kasan_kunit_test(); + /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */ + disable_trace_on_warning(); + /* Do not allow LOCKDEP mangling KASAN reports. */ + lockdep_off(); + /* Make sure we don't end up in loop. */ + report_suppress_start(); + spin_lock_irqsave(&report_lock, *flags); + pr_err("==================================================================\n"); +} + +static void end_report(unsigned long *flags, const void *addr, bool is_write) +{ + if (addr) + trace_error_report_end(ERROR_DETECTOR_KASAN, + (unsigned long)addr); + pr_err("==================================================================\n"); + spin_unlock_irqrestore(&report_lock, *flags); + if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) + check_panic_on_warn("KASAN"); + switch (kasan_arg_fault) { + case KASAN_ARG_FAULT_DEFAULT: + case KASAN_ARG_FAULT_REPORT: + break; + case KASAN_ARG_FAULT_PANIC: + panic("kasan.fault=panic set ...\n"); + break; + case KASAN_ARG_FAULT_PANIC_ON_WRITE: + if (is_write) + panic("kasan.fault=panic_on_write set ...\n"); + break; + } + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); + lockdep_on(); + report_suppress_stop(); +} + +static void print_error_description(struct kasan_report_info *info) +{ + pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip); + + if (info->type != KASAN_REPORT_ACCESS) { + pr_err("Free of addr %px by task %s/%d\n", + info->access_addr, current->comm, task_pid_nr(current)); + return; + } + + if (info->access_size) + pr_err("%s of size %zu at addr %px by task %s/%d\n", + info->is_write ? "Write" : "Read", info->access_size, + info->access_addr, current->comm, task_pid_nr(current)); + else + pr_err("%s at addr %px by task %s/%d\n", + info->is_write ? "Write" : "Read", + info->access_addr, current->comm, task_pid_nr(current)); +} + +static void print_track(struct kasan_track *track, const char *prefix) +{ + pr_err("%s by task %u:\n", prefix, track->pid); + if (track->stack) + stack_depot_print(track->stack); + else + pr_err("(stack is not available)\n"); +} + +static inline struct page *addr_to_page(const void *addr) +{ + if (virt_addr_valid(addr)) + return virt_to_head_page(addr); + return NULL; +} + +static void describe_object_addr(const void *addr, struct kasan_report_info *info) +{ + unsigned long access_addr = (unsigned long)addr; + unsigned long object_addr = (unsigned long)info->object; + const char *rel_type, *region_state = ""; + int rel_bytes; + + pr_err("The buggy address belongs to the object at %px\n" + " which belongs to the cache %s of size %d\n", + info->object, info->cache->name, info->cache->object_size); + + if (access_addr < object_addr) { + rel_type = "to the left"; + rel_bytes = object_addr - access_addr; + } else if (access_addr >= object_addr + info->alloc_size) { + rel_type = "to the right"; + rel_bytes = access_addr - (object_addr + info->alloc_size); + } else { + rel_type = "inside"; + rel_bytes = access_addr - object_addr; + } + + /* + * Tag-Based modes use the stack ring to infer the bug type, but the + * memory region state description is generated based on the metadata. + * Thus, defining the region state as below can contradict the metadata. + * Fixing this requires further improvements, so only infer the state + * for the Generic mode. + */ + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { + if (strcmp(info->bug_type, "slab-out-of-bounds") == 0) + region_state = "allocated "; + else if (strcmp(info->bug_type, "slab-use-after-free") == 0) + region_state = "freed "; + } + + pr_err("The buggy address is located %d bytes %s of\n" + " %s%zu-byte region [%px, %px)\n", + rel_bytes, rel_type, region_state, info->alloc_size, + (void *)object_addr, (void *)(object_addr + info->alloc_size)); +} + +static void describe_object_stacks(struct kasan_report_info *info) +{ + if (info->alloc_track.stack) { + print_track(&info->alloc_track, "Allocated"); + pr_err("\n"); + } + + if (info->free_track.stack) { + print_track(&info->free_track, "Freed"); + pr_err("\n"); + } + + kasan_print_aux_stacks(info->cache, info->object); +} + +static void describe_object(const void *addr, struct kasan_report_info *info) +{ + if (kasan_stack_collection_enabled()) + describe_object_stacks(info); + describe_object_addr(addr, info); +} + +static inline bool kernel_or_module_addr(const void *addr) +{ + if (is_kernel((unsigned long)addr)) + return true; + if (is_module_address((unsigned long)addr)) + return true; + return false; +} + +static inline bool init_task_stack_addr(const void *addr) +{ + return addr >= (void *)&init_thread_union.stack && + (addr <= (void *)&init_thread_union.stack + + sizeof(init_thread_union.stack)); +} + +static void print_address_description(void *addr, u8 tag, + struct kasan_report_info *info) +{ + struct page *page = addr_to_page(addr); + + dump_stack_lvl(KERN_ERR); + pr_err("\n"); + + if (info->cache && info->object) { + describe_object(addr, info); + pr_err("\n"); + } + + if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { + pr_err("The buggy address belongs to the variable:\n"); + pr_err(" %pS\n", addr); + pr_err("\n"); + } + + if (object_is_on_stack(addr)) { + /* + * Currently, KASAN supports printing frame information only + * for accesses to the task's own stack. + */ + kasan_print_address_stack_frame(addr); + pr_err("\n"); + } + + if (is_vmalloc_addr(addr)) { + struct vm_struct *va = find_vm_area(addr); + + if (va) { + pr_err("The buggy address belongs to the virtual mapping at\n" + " [%px, %px) created by:\n" + " %pS\n", + va->addr, va->addr + va->size, va->caller); + pr_err("\n"); + + page = vmalloc_to_page(addr); + } + } + + if (page) { + pr_err("The buggy address belongs to the physical page:\n"); + dump_page(page, "kasan: bad access detected"); + pr_err("\n"); + } +} + +static bool meta_row_is_guilty(const void *row, const void *addr) +{ + return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW); +} + +static int meta_pointer_offset(const void *row, const void *addr) +{ + /* + * Memory state around the buggy address: + * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe + * ... + * + * The length of ">ff00ff00ff00ff00: " is + * 3 + (BITS_PER_LONG / 8) * 2 chars. + * The length of each granule metadata is 2 bytes + * plus 1 byte for space. + */ + return 3 + (BITS_PER_LONG / 8) * 2 + + (addr - row) / KASAN_GRANULE_SIZE * 3 + 1; +} + +static void print_memory_metadata(const void *addr) +{ + int i; + void *row; + + row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW) + - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW; + + pr_err("Memory state around the buggy address:\n"); + + for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) { + char buffer[4 + (BITS_PER_LONG / 8) * 2]; + char metadata[META_BYTES_PER_ROW]; + + snprintf(buffer, sizeof(buffer), + (i == 0) ? ">%px: " : " %px: ", row); + + /* + * We should not pass a shadow pointer to generic + * function, because generic functions may try to + * access kasan mapping for the passed address. + */ + kasan_metadata_fetch_row(&metadata[0], row); + + print_hex_dump(KERN_ERR, buffer, + DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1, + metadata, META_BYTES_PER_ROW, 0); + + if (meta_row_is_guilty(row, addr)) + pr_err("%*c\n", meta_pointer_offset(row, addr), '^'); + + row += META_MEM_BYTES_PER_ROW; + } +} + +static void print_report(struct kasan_report_info *info) +{ + void *addr = kasan_reset_tag((void *)info->access_addr); + u8 tag = get_tag((void *)info->access_addr); + + print_error_description(info); + if (addr_has_metadata(addr)) + kasan_print_tags(tag, info->first_bad_addr); + pr_err("\n"); + + if (addr_has_metadata(addr)) { + print_address_description(addr, tag, info); + print_memory_metadata(info->first_bad_addr); + } else { + dump_stack_lvl(KERN_ERR); + } +} + +static void complete_report_info(struct kasan_report_info *info) +{ + void *addr = kasan_reset_tag((void *)info->access_addr); + struct slab *slab; + + if (info->type == KASAN_REPORT_ACCESS) + info->first_bad_addr = kasan_find_first_bad_addr( + (void *)info->access_addr, info->access_size); + else + info->first_bad_addr = addr; + + slab = kasan_addr_to_slab(addr); + if (slab) { + info->cache = slab->slab_cache; + info->object = nearest_obj(info->cache, slab, addr); + + /* Try to determine allocation size based on the metadata. */ + info->alloc_size = kasan_get_alloc_size(info->object, info->cache); + /* Fallback to the object size if failed. */ + if (!info->alloc_size) + info->alloc_size = info->cache->object_size; + } else + info->cache = info->object = NULL; + + switch (info->type) { + case KASAN_REPORT_INVALID_FREE: + info->bug_type = "invalid-free"; + break; + case KASAN_REPORT_DOUBLE_FREE: + info->bug_type = "double-free"; + break; + default: + /* bug_type filled in by kasan_complete_mode_report_info. */ + break; + } + + /* Fill in mode-specific report info fields. */ + kasan_complete_mode_report_info(info); +} + +void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type) +{ + unsigned long flags; + struct kasan_report_info info; + + /* + * Do not check report_suppressed_sw(), as an invalid-free cannot be + * caused by accessing poisoned memory and thus should not be suppressed + * by kasan_disable/enable_current() critical sections. + * + * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free() + * is triggered by explicit tag checks and not by the ones performed by + * the CPU. Thus, reporting invalid-free is not suppressed as well. + */ + if (unlikely(!report_enabled())) + return; + + start_report(&flags, true); + + memset(&info, 0, sizeof(info)); + info.type = type; + info.access_addr = ptr; + info.access_size = 0; + info.is_write = false; + info.ip = ip; + + complete_report_info(&info); + + print_report(&info); + + /* + * Invalid free is considered a "write" since the allocator's metadata + * updates involves writes. + */ + end_report(&flags, ptr, true); +} + +/* + * kasan_report() is the only reporting function that uses + * user_access_save/restore(): kasan_report_invalid_free() cannot be called + * from a UACCESS region, and kasan_report_async() is not used on x86. + */ +bool kasan_report(const void *addr, size_t size, bool is_write, + unsigned long ip) +{ + bool ret = true; + unsigned long ua_flags = user_access_save(); + unsigned long irq_flags; + struct kasan_report_info info; + + if (unlikely(report_suppressed_sw()) || unlikely(!report_enabled())) { + ret = false; + goto out; + } + + start_report(&irq_flags, true); + + memset(&info, 0, sizeof(info)); + info.type = KASAN_REPORT_ACCESS; + info.access_addr = addr; + info.access_size = size; + info.is_write = is_write; + info.ip = ip; + + complete_report_info(&info); + + print_report(&info); + + end_report(&irq_flags, (void *)addr, is_write); + +out: + user_access_restore(ua_flags); + + return ret; +} + +#ifdef CONFIG_KASAN_HW_TAGS +void kasan_report_async(void) +{ + unsigned long flags; + + /* + * Do not check report_suppressed_sw(), as + * kasan_disable/enable_current() critical sections do not affect + * Hardware Tag-Based KASAN. + */ + if (unlikely(!report_enabled())) + return; + + start_report(&flags, false); + pr_err("BUG: KASAN: invalid-access\n"); + pr_err("Asynchronous fault: no details available\n"); + pr_err("\n"); + dump_stack_lvl(KERN_ERR); + /* + * Conservatively set is_write=true, because no details are available. + * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic. + */ + end_report(&flags, NULL, true); +} +#endif /* CONFIG_KASAN_HW_TAGS */ + +#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) +/* + * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high + * canonical half of the address space) cause out-of-bounds shadow memory reads + * before the actual access. For addresses in the low canonical half of the + * address space, as well as most non-canonical addresses, that out-of-bounds + * shadow memory access lands in the non-canonical part of the address space. + * Help the user figure out what the original bogus pointer was. + */ +void kasan_non_canonical_hook(unsigned long addr) +{ + unsigned long orig_addr; + const char *bug_type; + + if (addr < KASAN_SHADOW_OFFSET) + return; + + orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT; + /* + * For faults near the shadow address for NULL, we can be fairly certain + * that this is a KASAN shadow memory access. + * For faults that correspond to shadow for low canonical addresses, we + * can still be pretty sure - that shadow region is a fairly narrow + * chunk of the non-canonical address space. + * But faults that look like shadow for non-canonical addresses are a + * really large chunk of the address space. In that case, we still + * print the decoded address, but make it clear that this is not + * necessarily what's actually going on. + */ + if (orig_addr < PAGE_SIZE) + bug_type = "null-ptr-deref"; + else if (orig_addr < TASK_SIZE) + bug_type = "probably user-memory-access"; + else + bug_type = "maybe wild-memory-access"; + pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type, + orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1); +} +#endif |