Messages in this thread Patch in this message | | | From | Peng Zhang <> | Subject | [PATCH v2] fscache: fix OOB Read in __fscache_acquire_volume | Date | Tue, 15 Nov 2022 14:04:47 +0000 |
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From: ZhangPeng <zhangpeng362@huawei.com>
Syzbot reported slab-out-of-bounds Read in __fscache_acquire_volume.
================================================================== 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
CPU: 0 PID: 3613 Comm: syz-executor344 Not tainted 6.0.0-rc2-syzkaller-00327-g8379c0b31fbc #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x719 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 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 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f7d5064b1d9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd1700c028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007ffd1700c060 RCX: 00007f7d5064b1d9 RDX: 0000000020000040 RSI: 0000000020000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000020000200 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000f4240 R13: 0000000000000000 R14: 00007ffd1700c04c R15: 00007ffd1700c050 ==================================================================
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. Fix this by adding a check on the length of the key in fscache_alloc_volume(). --- v1 -> v2: - Make sure the length of cache volume key (klen) fits a signed char before writing key[0] that'd benefit everyone, thanks to Dominique Martinet.
Reported-by: syzbot+a76f6a6e524cf2080aa3@syzkaller.appspotmail.com Fixes: 62ab63352350 ("fscache: Implement volume registration") Signed-off-by: ZhangPeng <zhangpeng362@huawei.com> --- fs/fscache/volume.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c index a058e0136bfe..cc206d5e4cc7 100644 --- a/fs/fscache/volume.c +++ b/fs/fscache/volume.c @@ -230,6 +230,8 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key, * hashing easier. */ klen = strlen(volume_key); + if (klen > 127) + goto err_cache; hlen = round_up(1 + klen + 1, sizeof(__le32)); key = kzalloc(hlen, GFP_KERNEL); if (!key) -- 2.25.1
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