On 12.03.19 г. 9:45 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 > > For the first time tree read, it will not pass verify_level_key() check. > But the extent buffer will still be cached. > > Also there is a pitfall in read_block_for_search(), where a cached > extent buffer will not be checked for its level and first key. > > There are context where we read tree block without verifying its > first key, such as scrub. > > So in that case, a corrupted leaf can sneak in and screw up the kernel. > > [FIX] > Export verify_level_key() as btrfs_verify_level_key() and call it in > read_block_for_search() to fill the hole. > > Please note, this will cause a lot of extra error message if we have a > bad tree block in any hot tree, but it's still much better to trigger > the final safe net in key_search_validate(). > > 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> Additionally which of those 6 issues contain the image which triggers this problem or all of them ? > --- > There is one remaining report where I can't get any kernel message > before the VM completely lost reponse. > https://bugzilla.kernel.org/show_bug.cgi?id=202763 > (out-of-bound access in end_bio_extent_readpage() when mounting and operating a crafted btrfs image) > > And the above case can't be fixed by this patch. Still trying to get a > good idea of what's going wrong (AKA good kernel message). > > There is also another report, which doesn't provide the fuzzed image. > https://bugzilla.kernel.org/show_bug.cgi?id=202765 > (NULL pointer dereference when mounting a crafted btrfs image) > --- > 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..37447a7c5b4d 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, as it's possible the > + * eb is read from the context without first_key > + * requirement > + */ > + 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); >
