On 13.03.19 г. 10:55 ч., Qu Wenruo wrote: > [BUG] > When reading a file from a fuzzed image, kernel can panic like: > BTRFS warning (device loop0): csum failed root 5 ino 270 off 0 csum 0x98f94189 expected csum 0x00000000 mirror 1 > assertion failed: !memcmp_extent_buffer(b, &disk_key, offsetof(struct btrfs_leaf, items[0].key), sizeof(disk_key)), file: fs/btrfs/ctree.c, line: 2544 > ------------[ cut here ]------------ > kernel BUG at fs/btrfs/ctree.h:3500! > invalid opcode: 0000 [#1] PREEMPT SMP NOPTI > RIP: 0010:btrfs_search_slot.cold.24+0x61/0x63 [btrfs] > Call Trace: > btrfs_lookup_csum+0x52/0x150 [btrfs] > __btrfs_lookup_bio_sums+0x209/0x640 [btrfs] > btrfs_submit_bio_hook+0x103/0x170 [btrfs] > submit_one_bio+0x59/0x80 [btrfs] > extent_read_full_page+0x58/0x80 [btrfs] > generic_file_read_iter+0x2f6/0x9d0 > __vfs_read+0x14d/0x1a0 > vfs_read+0x8d/0x140 > ksys_read+0x52/0xc0 > do_syscall_64+0x60/0x210 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > [CAUSE] > The fuzzed image has a corrupted leaf whose first key doesn't match with its parent: > checksum tree key (CSUM_TREE ROOT_ITEM 0) > node 29741056 level 1 items 14 free 107 generation 19 owner CSUM_TREE > fs uuid 3381d111-94a3-4ac7-8f39-611bbbdab7e6 > chunk uuid 9af1c3c7-2af5-488b-8553-530bd515f14c > ... > key (EXTENT_CSUM EXTENT_CSUM 79691776) block 29761536 gen 19 > > leaf 29761536 items 1 free space 1726 generation 19 owner CSUM_TREE > leaf 29761536 flags 0x1(WRITTEN) backref revision 1 > fs uuid 3381d111-94a3-4ac7-8f39-611bbbdab7e6 > chunk uuid 9af1c3c7-2af5-488b-8553-530bd515f14c > item 0 key (EXTENT_CSUM EXTENT_CSUM 8798638964736) itemoff 1751 itemsize 2244 > range start 8798638964736 end 8798641262592 length 2297856 > > When reading above tree block, we have extent_buffer->refs = 2 in the > context: > - initial one from __alloc_extent_buffer() > alloc_extent_buffer() > |- __alloc_extent_buffer() > |- atomic_set(&eb->refs, 1) > > - one being added to fs_info->buffer_radix > alloc_extent_buffer() > |- check_buffer_tree_ref() > |- atomic_inc(&eb->refs) > > So even we call free_extent_buffer() in read_tree_block or other similar > situation, we only decrease the refs by 1, it doesn't reach 0 and won't > be freed right now. > > The staled eb and its corrupted content will still be kept cached. > > Further more, we have several extra cases where we either don't do > first key check or the check is not proper for all callers: > - scrub > We just don't have first key in this context. > > - shared tree block > One tree block can be shared by several snapshot/subvolume trees. > In that case, the first key check for one subvolume doesn't apply to > another. > > So for above reasons, a corrupted extent buffer can sneak into the > buffer cache. > > [FIX] > Export verify_level_key() as btrfs_verify_level_key() and call it in > read_block_for_search() to fill the hole. > > Due to above described reasons, even we can free corrupted extent buffer > from cache, we still need the check in read_block_for_search(), for > scrub and shared tree blocks. > > Reported-by: Yoon Jungyeon <jungyeon@xxxxxxxxxx> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202755 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202757 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202759 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202761 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202767 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202769 > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > --- I had already reviewed the earlier posting of this patch so: Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx> > fs/btrfs/ctree.c | 10 ++++++++++ > fs/btrfs/disk-io.c | 10 +++++----- > fs/btrfs/disk-io.h | 3 +++ > 3 files changed, 18 insertions(+), 5 deletions(-) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index 5a6c39b44c84..7672932aa5b4 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -2401,6 +2401,16 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p, > if (tmp) { > /* first we do an atomic uptodate check */ > if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) { > + /* > + * Do extra check for first_key, eb can be stale due to > + * being cached, read from scrub, or have multiple > + * parents (shared tree blocks). > + */ > + if (btrfs_verify_level_key(fs_info, tmp, > + parent_level - 1, &first_key, gen)) { > + free_extent_buffer(tmp); > + return -EUCLEAN; > + } > *eb_ret = tmp; > return 0; > } > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 298b34721bc0..e2a0cb362d28 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -423,9 +423,9 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info, > return ret; > } > > -static int verify_level_key(struct btrfs_fs_info *fs_info, > - struct extent_buffer *eb, int level, > - struct btrfs_key *first_key, u64 parent_transid) > +int btrfs_verify_level_key(struct btrfs_fs_info *fs_info, > + struct extent_buffer *eb, int level, > + struct btrfs_key *first_key, u64 parent_transid) > { > int found_level; > struct btrfs_key found_key; > @@ -500,8 +500,8 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info, > if (verify_parent_transid(io_tree, eb, > parent_transid, 0)) > ret = -EIO; > - else if (verify_level_key(fs_info, eb, level, > - first_key, parent_transid)) > + else if (btrfs_verify_level_key(fs_info, eb, level, > + first_key, parent_transid)) > ret = -EUCLEAN; > else > break; > diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h > index 987a64bc0c66..67a9fe2d29c7 100644 > --- a/fs/btrfs/disk-io.h > +++ b/fs/btrfs/disk-io.h > @@ -39,6 +39,9 @@ static inline u64 btrfs_sb_offset(int mirror) > struct btrfs_device; > struct btrfs_fs_devices; > > +int btrfs_verify_level_key(struct btrfs_fs_info *fs_info, > + struct extent_buffer *eb, int level, > + struct btrfs_key *first_key, u64 parent_transid); > struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr, > u64 parent_transid, int level, > struct btrfs_key *first_key); >
