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fscache: fix OOB Read in __fscache_acquire_volume
[ Upstream commit9f0933ac02
] The type of a->key[0] is char in fscache_volume_same(). If the length of cache volume key is greater than 127, the value of a->key[0] is less than 0. In this case, klen becomes much larger than 255 after type conversion, because the type of klen is size_t. As a result, memcmp() is read out of bounds. This causes a slab-out-of-bounds Read in __fscache_acquire_volume(), as reported by Syzbot. Fix this by changing the type of the stored key to "u8 *" rather than "char *" (it isn't a simple string anyway). Also put in a check that the volume name doesn't exceed NAME_MAX. BUG: KASAN: slab-out-of-bounds in memcmp+0x16f/0x1c0 lib/string.c:757 Read of size 8 at addr ffff888016f3aa90 by task syz-executor344/3613 Call Trace: memcmp+0x16f/0x1c0 lib/string.c:757 memcmp include/linux/fortify-string.h:420 [inline] fscache_volume_same fs/fscache/volume.c:133 [inline] fscache_hash_volume fs/fscache/volume.c:171 [inline] __fscache_acquire_volume+0x76c/0x1080 fs/fscache/volume.c:328 fscache_acquire_volume include/linux/fscache.h:204 [inline] v9fs_cache_session_get_cookie+0x143/0x240 fs/9p/cache.c:34 v9fs_session_init+0x1166/0x1810 fs/9p/v9fs.c:473 v9fs_mount+0xba/0xc90 fs/9p/vfs_super.c:126 legacy_get_tree+0x105/0x220 fs/fs_context.c:610 vfs_get_tree+0x89/0x2f0 fs/super.c:1530 do_new_mount fs/namespace.c:3040 [inline] path_mount+0x1326/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline] __do_sys_mount fs/namespace.c:3591 [inline] __se_sys_mount fs/namespace.c:3568 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 Fixes:62ab633523
("fscache: Implement volume registration") Reported-by: syzbot+a76f6a6e524cf2080aa3@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Zhang Peng <zhangpeng362@huawei.com> Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com> cc: Dominique Martinet <asmadeus@codewreck.org> cc: Jeff Layton <jlayton@kernel.org> cc: v9fs-developer@lists.sourceforge.net cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/Y3OH+Dmi0QIOK18n@codewreck.org/ # Zhang Peng's v1 fix Link: https://lore.kernel.org/r/20221115140447.2971680-1-zhangpeng362@huawei.com/ # Zhang Peng's v2 fix Link: https://lore.kernel.org/r/166869954095.3793579.8500020902371015443.stgit@warthog.procyon.org.uk/ # v1 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit
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2 changed files with 6 additions and 3 deletions
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@ -203,7 +203,11 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key,
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struct fscache_volume *volume;
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struct fscache_cache *cache;
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size_t klen, hlen;
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char *key;
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u8 *key;
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klen = strlen(volume_key);
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if (klen > NAME_MAX)
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return NULL;
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if (!coherency_data)
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coherency_len = 0;
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@ -229,7 +233,6 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key,
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/* Stick the length on the front of the key and pad it out to make
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* hashing easier.
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*/
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klen = strlen(volume_key);
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hlen = round_up(1 + klen + 1, sizeof(__le32));
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key = kzalloc(hlen, GFP_KERNEL);
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if (!key)
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@ -75,7 +75,7 @@ struct fscache_volume {
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atomic_t n_accesses; /* Number of cache accesses in progress */
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unsigned int debug_id;
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unsigned int key_hash; /* Hash of key string */
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char *key; /* Volume ID, eg. "afs@example.com@1234" */
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u8 *key; /* Volume ID, eg. "afs@example.com@1234" */
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struct list_head proc_link; /* Link in /proc/fs/fscache/volumes */
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struct hlist_bl_node hash_link; /* Link in hash table */
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struct work_struct work;
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