From nobody Wed Nov 13 06:57:39 2024 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04D91C61D97 for ; Sun, 29 Jan 2023 02:15:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233219AbjA2CP6 (ORCPT ); Sat, 28 Jan 2023 21:15:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229749AbjA2CPz (ORCPT ); Sat, 28 Jan 2023 21:15:55 -0500 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DF1322DDD for ; Sat, 28 Jan 2023 18:15:52 -0800 (PST) X-UUID: d72321f89f7a11eda06fc9ecc4dadd91-20230129 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=XhHmJ2XlHdSznR6d+1zWQZ89NMCKCkYujHZawrbnfto=; b=nRPuXgax0T4hV98h/7Wjn2En6Oa6PkX2uqNvUe9zKCIp2q5rB5TZFmX8lkJLDNWgzcGaj66QkAD1GSJ4Y9YWt9JyDHb7m8m8ukvsr9m/3ohoDRchHI3jcKeWDpysU8wJjAIz3hSdBrh3iLPXsVjRHpEn8rYJWnryDVzmGtW6pvQ=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.18,REQID:80850fa4-3b81-4ed5-98fa-4f9352435c7a,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:3ca2d6b,CLOUDID:e4d9a055-dd49-462e-a4be-2143a3ddc739,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:1,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0 X-CID-BVR: 0 X-UUID: d72321f89f7a11eda06fc9ecc4dadd91-20230129 Received: from mtkmbs10n2.mediatek.inc [(172.21.101.183)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 530970514; Sun, 29 Jan 2023 10:15:46 +0800 Received: from mtkmbs13n1.mediatek.inc (172.21.101.193) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.792.3; Sun, 29 Jan 2023 10:15:44 +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; Sun, 29 Jan 2023 10:15:44 +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 v4] kasan: infer allocation size by scanning metadata Date: Sun, 29 Jan 2023 10:14:35 +0800 Message-ID: <20230129021437.18812-1-Kuan-Ying.Lee@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Make KASAN scan metadata to infer the requested allocation size instead of printing cache->object_size. This patch fixes confusing slab-out-of-bounds reports as reported in: https://bugzilla.kernel.org/show_bug.cgi?id=3D216457 As an example of the confusing behavior, the report below hints that the allocation size was 192, while the kernel actually called kmalloc(184): =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 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 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D With this patch, the report shows: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ... 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 to the right of allocated 184-byte region [ffff888017576600, ffff8880175766b8) ... =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Also report slab use-after-free bugs as "slab-use-after-free" and print "freed" instead of "allocated" in the report when describing the accessed memory region. Also improve the metadata-related comment in kasan_find_first_bad_addr and use addr_has_metadata across KASAN code instead of open-coding KASAN_SHADOW_START checks. Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D216457 Co-developed-by: Andrey Konovalov Signed-off-by: Kuan-Ying Lee --- Changes v3->v4: - Change the author Changes v2->v3: - Rename obj_size to alloc_size and change its type to size_t. - Add comments into kasan_get_alloc_size. - Infer and report alloc_size for all report types. - Update metadata-related comment in kasan_find_first_bad_addr for HW_TAGS. - Use addr_has_metadata for Generic and SW_TAGS modes instead of open-coding KASAN_SHADOW_START checks. - Introduce slab-use-after-free report type. - Print "freed" when describing memory region for slab-use-after-free bugs. - Only print memory region state for Generic mode. Changes 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/generic.c | 4 +--- mm/kasan/kasan.h | 2 ++ mm/kasan/report.c | 41 ++++++++++++++++++++++++++++----------- mm/kasan/report_generic.c | 32 +++++++++++++++++++++++++++++- mm/kasan/report_hw_tags.c | 35 ++++++++++++++++++++++++++++++++- mm/kasan/report_sw_tags.c | 26 +++++++++++++++++++++++++ mm/kasan/report_tags.c | 2 +- mm/kasan/sw_tags.c | 6 ++---- 8 files changed, 127 insertions(+), 21 deletions(-) diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index cb762982c8ba..e5eef670735e 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -172,10 +172,8 @@ static __always_inline bool check_region_inline(unsign= ed long addr, if (unlikely(addr + size < addr)) return !kasan_report(addr, size, write, ret_ip); =20 - if (unlikely((void *)addr < - kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { + if (unlikely(!addr_has_metadata((void *)addr))) return !kasan_report(addr, size, write, ret_ip); - } =20 if (likely(!memory_is_poisoned(addr, size))) return true; diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index dcc2a88e8121..3231314e071f 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -207,6 +207,7 @@ struct kasan_report_info { void *first_bad_addr; struct kmem_cache *cache; void *object; + size_t alloc_size; =20 /* Filled in by the mode-specific reporting code. */ const char *bug_type; @@ -323,6 +324,7 @@ static inline bool addr_has_metadata(const void *addr) #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ =20 void *kasan_find_first_bad_addr(void *addr, size_t size); +size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache); void kasan_complete_mode_report_info(struct kasan_report_info *info); void kasan_metadata_fetch_row(char *buffer, void *row); =20 diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 22598b20c7b7..e0492124e90a 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -231,33 +231,46 @@ static inline struct page *addr_to_page(const void *a= ddr) return NULL; } =20 -static void describe_object_addr(const void *addr, struct kmem_cache *cach= e, - void *object) +static void describe_object_addr(const void *addr, struct kasan_report_inf= o *info) { unsigned long access_addr =3D (unsigned long)addr; - unsigned long object_addr =3D (unsigned long)object; - const char *rel_type; + unsigned long object_addr =3D (unsigned long)info->object; + const char *rel_type, *region_state =3D ""; int rel_bytes; =20 pr_err("The buggy address belongs to the object at %px\n" " which belongs to the cache %s of size %d\n", - object, cache->name, cache->object_size); + info->object, info->cache->name, info->cache->object_size); =20 if (access_addr < object_addr) { rel_type =3D "to the left"; rel_bytes =3D object_addr - access_addr; - } else if (access_addr >=3D object_addr + cache->object_size) { + } else if (access_addr >=3D object_addr + info->alloc_size) { rel_type =3D "to the right"; - rel_bytes =3D access_addr - (object_addr + cache->object_size); + rel_bytes =3D access_addr - (object_addr + info->alloc_size); } else { rel_type =3D "inside"; rel_bytes =3D access_addr - object_addr; } =20 + /* + * 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") =3D=3D 0) + region_state =3D "allocated "; + else if (strcmp(info->bug_type, "slab-use-after-free") =3D=3D 0) + region_state =3D "freed "; + } + 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%lu-byte region [%px, %px)\n", + rel_bytes, rel_type, region_state, info->alloc_size, + (void *)object_addr, (void *)(object_addr + info->alloc_size)); } =20 static void describe_object_stacks(struct kasan_report_info *info) @@ -279,7 +292,7 @@ static void describe_object(const void *addr, struct ka= san_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); } =20 static inline bool kernel_or_module_addr(const void *addr) @@ -436,6 +449,12 @@ static void complete_report_info(struct kasan_report_i= nfo *info) if (slab) { info->cache =3D slab->slab_cache; info->object =3D nearest_obj(info->cache, slab, addr); + + /* Try to determine allocation size based on the metadata. */ + info->alloc_size =3D kasan_get_alloc_size(info->object, info->cache); + /* Fallback to the object size if failed. */ + if (!info->alloc_size) + info->alloc_size =3D info->cache->object_size; } else info->cache =3D info->object =3D NULL; =20 diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c index 043c94b04605..87d39bc0a673 100644 --- a/mm/kasan/report_generic.c +++ b/mm/kasan/report_generic.c @@ -43,6 +43,34 @@ void *kasan_find_first_bad_addr(void *addr, size_t size) return p; } =20 +size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache) +{ + size_t size =3D 0; + u8 *shadow; + + /* + * Skip the addr_has_metadata check, as this function only operates on + * slab memory, which must have metadata. + */ + + /* + * The loop below returns 0 for freed objects, for which KASAN cannot + * calculate the allocation size based on the metadata. + */ + shadow =3D (u8 *)kasan_mem_to_shadow(object); + while (size < cache->object_size) { + if (*shadow =3D=3D 0) + size +=3D KASAN_GRANULE_SIZE; + else if (*shadow >=3D 1 && *shadow <=3D KASAN_GRANULE_SIZE - 1) + return 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 =3D "unknown-crash"; @@ -79,9 +107,11 @@ static const char *get_shadow_bug_type(struct kasan_rep= ort_info *info) bug_type =3D "stack-out-of-bounds"; break; case KASAN_PAGE_FREE: + bug_type =3D "use-after-free"; + break; case KASAN_SLAB_FREE: case KASAN_SLAB_FREETRACK: - bug_type =3D "use-after-free"; + bug_type =3D "slab-use-after-free"; break; case KASAN_ALLOCA_LEFT: case KASAN_ALLOCA_RIGHT: diff --git a/mm/kasan/report_hw_tags.c b/mm/kasan/report_hw_tags.c index f3d3be614e4b..32e80f78de7d 100644 --- a/mm/kasan/report_hw_tags.c +++ b/mm/kasan/report_hw_tags.c @@ -17,10 +17,43 @@ =20 void *kasan_find_first_bad_addr(void *addr, size_t size) { - /* Return the same value regardless of whether addr_has_metadata(). */ + /* + * Hardware Tag-Based KASAN only calls this function for normal memory + * accesses, and thus addr points precisely to the first bad address + * with an invalid (and present) memory tag. Therefore: + * 1. Return the address as is without walking memory tags. + * 2. Skip the addr_has_metadata check. + */ return kasan_reset_tag(addr); } =20 +size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache) +{ + size_t size =3D 0; + int i =3D 0; + u8 memory_tag; + + /* + * Skip the addr_has_metadata check, as this function only operates on + * slab memory, which must have metadata. + */ + + /* + * The loop below returns 0 for freed objects, for which KASAN cannot + * calculate the allocation size based on the metadata. + */ + while (size < cache->object_size) { + memory_tag =3D hw_get_mem_tag(object + i * KASAN_GRANULE_SIZE); + if (memory_tag !=3D KASAN_TAG_INVALID) + size +=3D 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..8b1f5a73ee6d 100644 --- a/mm/kasan/report_sw_tags.c +++ b/mm/kasan/report_sw_tags.c @@ -45,6 +45,32 @@ void *kasan_find_first_bad_addr(void *addr, size_t size) return p; } =20 +size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache) +{ + size_t size =3D 0; + u8 *shadow; + + /* + * Skip the addr_has_metadata check, as this function only operates on + * slab memory, which must have metadata. + */ + + /* + * The loop below returns 0 for freed objects, for which KASAN cannot + * calculate the allocation size based on the metadata. + */ + shadow =3D (u8 *)kasan_mem_to_shadow(object); + while (size < cache->object_size) { + if (*shadow !=3D KASAN_TAG_INVALID) + size +=3D 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..8b8bfdb3cfdb 100644 --- a/mm/kasan/report_tags.c +++ b/mm/kasan/report_tags.c @@ -89,7 +89,7 @@ void kasan_complete_mode_report_info(struct kasan_report_= info *info) * a use-after-free. */ if (!info->bug_type) - info->bug_type =3D "use-after-free"; + info->bug_type =3D "slab-use-after-free"; } else { /* Second alloc of the same object. Give up. */ if (alloc_found) diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c index a3afaf2ad1b1..30da65fa02a1 100644 --- a/mm/kasan/sw_tags.c +++ b/mm/kasan/sw_tags.c @@ -106,10 +106,8 @@ bool kasan_check_range(unsigned long addr, size_t size= , bool write, return true; =20 untagged_addr =3D kasan_reset_tag((const void *)addr); - if (unlikely(untagged_addr < - kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { + if (unlikely(!addr_has_metadata(untagged_addr))) return !kasan_report(addr, size, write, ret_ip); - } shadow_first =3D kasan_mem_to_shadow(untagged_addr); shadow_last =3D kasan_mem_to_shadow(untagged_addr + size - 1); for (shadow =3D shadow_first; shadow <=3D shadow_last; shadow++) { @@ -127,7 +125,7 @@ bool kasan_byte_accessible(const void *addr) void *untagged_addr =3D kasan_reset_tag(addr); u8 shadow_byte; =20 - if (untagged_addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) + if (!addr_has_metadata(untagged_addr)) return false; =20 shadow_byte =3D READ_ONCE(*(u8 *)kasan_mem_to_shadow(untagged_addr)); --=20 2.18.0