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Wed, 18 Jan 2023 17:38:57 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs13n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.792.15 via Frontend Transport; Wed, 18 Jan 2023 17:38:57 +0800 From: Kuan-Ying Lee To: Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , "Andrew Morton" , Matthias Brugger CC: , , Kuan-Ying Lee , , , , , Subject: [PATCH v2] kasan: infer the requested size by scanning shadow memory Date: Wed, 18 Jan 2023 17:38:30 +0800 Message-ID: <20230118093832.1945-1-Kuan-Ying.Lee@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230118_095437_690301_DDC3B5D8 X-CRM114-Status: GOOD ( 19.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org We scan the shadow memory to infer the requested size instead of printing cache->object_size directly. This patch will fix the confusing kasan slab-out-of-bounds report like below. [1] Report shows "cache kmalloc-192 of size 192", but user actually kmalloc(184). ================================================================== BUG: KASAN: slab-out-of-bounds in _find_next_bit+0x143/0x160 lib/find_bit.c:109 Read of size 8 at addr ffff8880175766b8 by task kworker/1:1/26 ... The buggy address belongs to the object at ffff888017576600 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 184 bytes inside of 192-byte region [ffff888017576600, ffff8880175766c0) ... Memory state around the buggy address: ffff888017576580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff888017576600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888017576680: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc ^ ffff888017576700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888017576780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== After this patch, slab-out-of-bounds report will show as below. ================================================================== ... The buggy address belongs to the object at ffff888017576600 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 0 bytes right of allocated 184-byte region [ffff888017576600, ffff8880175766b8) ... ================================================================== Link: https://bugzilla.kernel.org/show_bug.cgi?id=216457 [1] Signed-off-by: Kuan-Ying Lee --- V1 -> V2: - Implement getting allocated size of object for tag-based kasan. - Refine the kasan report. - Check if it is slab-out-of-bounds report type. - Thanks for Andrey and Dmitry suggestion. mm/kasan/kasan.h | 2 ++ mm/kasan/report.c | 20 +++++++++++++------- mm/kasan/report_generic.c | 24 ++++++++++++++++++++++++ mm/kasan/report_hw_tags.c | 18 ++++++++++++++++++ mm/kasan/report_sw_tags.c | 17 +++++++++++++++++ mm/kasan/report_tags.c | 8 ++++++++ 6 files changed, 82 insertions(+), 7 deletions(-) diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index abbcc1b0eec5..15ffd46fec6a 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -185,6 +185,7 @@ struct kasan_report_info { const char *bug_type; struct kasan_track alloc_track; struct kasan_track free_track; + int obj_size; }; /* Do not change the struct layout: compiler ABI. */ @@ -306,6 +307,7 @@ static inline bool addr_has_metadata(const void *addr) void *kasan_find_first_bad_addr(void *addr, size_t size); void kasan_complete_mode_report_info(struct kasan_report_info *info); void kasan_metadata_fetch_row(char *buffer, void *row); +int kasan_get_alloc_size(void *object_addr, struct kmem_cache *cache); #if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) void kasan_print_tags(u8 addr_tag, const void *addr); diff --git a/mm/kasan/report.c b/mm/kasan/report.c index df3602062bfd..dae0d4ae8fe9 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -210,12 +210,13 @@ static inline struct page *addr_to_page(const void *addr) } static void describe_object_addr(const void *addr, struct kmem_cache *cache, - void *object) + void *object, int obj_size, const char *bug_type) { unsigned long access_addr = (unsigned long)addr; unsigned long object_addr = (unsigned long)object; const char *rel_type; int rel_bytes; + bool slab_oob = false; pr_err("The buggy address belongs to the object at %px\n" " which belongs to the cache %s of size %d\n", @@ -224,18 +225,22 @@ static void describe_object_addr(const void *addr, struct kmem_cache *cache, if (access_addr < object_addr) { rel_type = "to the left"; rel_bytes = object_addr - access_addr; - } else if (access_addr >= object_addr + cache->object_size) { + } else if (access_addr >= object_addr + obj_size) { rel_type = "to the right"; - rel_bytes = access_addr - (object_addr + cache->object_size); + rel_bytes = access_addr - (object_addr + obj_size); } else { rel_type = "inside"; rel_bytes = access_addr - object_addr; } + if (strcmp(bug_type, "slab-out-of-bounds") == 0) + slab_oob = true; + pr_err("The buggy address is located %d bytes %s of\n" - " %d-byte region [%px, %px)\n", - rel_bytes, rel_type, cache->object_size, (void *)object_addr, - (void *)(object_addr + cache->object_size)); + " %s%d-byte region [%px, %px)\n", + rel_bytes, rel_type, slab_oob ? "allocated " : "", + obj_size, (void *)object_addr, + (void *)(object_addr + obj_size)); } static void describe_object_stacks(struct kasan_report_info *info) @@ -257,7 +262,8 @@ 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->cache, info->object); + describe_object_addr(addr, info->cache, info->object, info->obj_size, + info->bug_type); } static inline bool kernel_or_module_addr(const void *addr) diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c index 043c94b04605..7b4bec9e6d1a 100644 --- a/mm/kasan/report_generic.c +++ b/mm/kasan/report_generic.c @@ -43,6 +43,25 @@ void *kasan_find_first_bad_addr(void *addr, size_t size) return p; } +int kasan_get_alloc_size(void *addr, struct kmem_cache *cache) +{ + int size = 0; + u8 *shadow; + + shadow = (u8 *)kasan_mem_to_shadow(addr); + while (size < cache->object_size) { + if (*shadow == 0) + size += KASAN_GRANULE_SIZE; + else if (*shadow >= 1 && *shadow <= KASAN_GRANULE_SIZE - 1) + size += *shadow; + else + return size; + shadow++; + } + + return cache->object_size; +} + static const char *get_shadow_bug_type(struct kasan_report_info *info) { const char *bug_type = "unknown-crash"; @@ -149,6 +168,11 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info) memcpy(&info->free_track, &free_meta->free_track, sizeof(info->free_track)); } + + if (strcmp(info->bug_type, "slab-out-of-bounds") == 0) + info->obj_size = kasan_get_alloc_size(info->object, info->cache); + else + info->obj_size = info->cache->object_size; } void kasan_metadata_fetch_row(char *buffer, void *row) diff --git a/mm/kasan/report_hw_tags.c b/mm/kasan/report_hw_tags.c index f3d3be614e4b..e462dd750fe2 100644 --- a/mm/kasan/report_hw_tags.c +++ b/mm/kasan/report_hw_tags.c @@ -21,6 +21,24 @@ void *kasan_find_first_bad_addr(void *addr, size_t size) return kasan_reset_tag(addr); } +int kasan_get_alloc_size(void *addr, struct kmem_cache *cache) +{ + int size = 0, i = 0; + u8 memory_tag; + + while (size < cache->object_size) { + memory_tag = hw_get_mem_tag(addr + i * KASAN_GRANULE_SIZE); + + if (memory_tag != KASAN_TAG_INVALID) + size += KASAN_GRANULE_SIZE; + else + return size; + i++; + } + + return cache->object_size; +} + void kasan_metadata_fetch_row(char *buffer, void *row) { int i; diff --git a/mm/kasan/report_sw_tags.c b/mm/kasan/report_sw_tags.c index 7a26397297ed..d50caefd7fd5 100644 --- a/mm/kasan/report_sw_tags.c +++ b/mm/kasan/report_sw_tags.c @@ -45,6 +45,23 @@ void *kasan_find_first_bad_addr(void *addr, size_t size) return p; } +int kasan_get_alloc_size(void *addr, struct kmem_cache *cache) +{ + int size = 0; + u8 *shadow; + + shadow = (u8 *)kasan_mem_to_shadow(addr); + while (size < cache->object_size) { + if (*shadow != KASAN_TAG_INVALID) + size += KASAN_GRANULE_SIZE; + else + return size; + shadow++; + } + + return cache->object_size; +} + void kasan_metadata_fetch_row(char *buffer, void *row) { memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW); diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c index ecede06ef374..b349a0ae1b83 100644 --- a/mm/kasan/report_tags.c +++ b/mm/kasan/report_tags.c @@ -7,6 +7,7 @@ #include #include "kasan.h" +#include "../slab.h" extern struct kasan_stack_ring stack_ring; @@ -113,4 +114,11 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info) /* Assign the common bug type if no entries were found. */ if (!info->bug_type) info->bug_type = get_common_bug_type(info); + + if (info->object && info->cache) { + if (strcmp(info->bug_type, "slab-out-of-bounds") == 0) + info->obj_size = kasan_get_alloc_size(info->object, info->cache); + else + info->obj_size = info->cache->object_size; + } }