On 2019/7/25 下午5:26, Nikolay Borisov wrote: > > > On 25.07.19 г. 9:12 ч., Qu Wenruo wrote: >> [BUG] >> With crafted image, btrfs will panic at btree operations: >> kernel BUG at fs/btrfs/ctree.c:3894! >> invalid opcode: 0000 [#1] SMP PTI >> CPU: 0 PID: 1138 Comm: btrfs-transacti Not tainted 5.0.0-rc8+ #9 >> RIP: 0010:__push_leaf_left+0x6b6/0x6e0 >> Code: 00 00 48 98 48 8d 04 80 48 8d 74 80 65 e8 42 5a 04 00 48 8b bd 78 ff ff ff 8b bf 90 d0 00 00 89 7d 98 83 ef 65 e9 06 ff ff ff <0f> 0b 0f 0b 48 8b 85 78 ff ff ff 8b 90 90 d0 00 00 e9 eb fe ff ff >> RSP: 0018:ffffc0bd4128b990 EFLAGS: 00010246 >> RAX: 0000000000000000 RBX: ffffa0a4ab8f0e38 RCX: 0000000000000000 >> RDX: ffffa0a280000000 RSI: 0000000000000000 RDI: ffffa0a4b3814000 >> RBP: ffffc0bd4128ba38 R08: 0000000000001000 R09: ffffc0bd4128b948 >> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000240 >> R13: ffffa0a4b556fb60 R14: ffffa0a4ab8f0af0 R15: ffffa0a4ab8f0af0 >> FS: 0000000000000000(0000) GS:ffffa0a4b7a00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007f2461c80020 CR3: 000000022b32a006 CR4: 00000000000206f0 >> Call Trace: >> ? _cond_resched+0x1a/0x50 >> push_leaf_left+0x179/0x190 >> btrfs_del_items+0x316/0x470 >> btrfs_del_csums+0x215/0x3a0 >> __btrfs_free_extent.isra.72+0x5a7/0xbe0 >> __btrfs_run_delayed_refs+0x539/0x1120 >> btrfs_run_delayed_refs+0xdb/0x1b0 >> btrfs_commit_transaction+0x52/0x950 >> ? start_transaction+0x94/0x450 >> transaction_kthread+0x163/0x190 >> kthread+0x105/0x140 >> ? btrfs_cleanup_transaction+0x560/0x560 >> ? kthread_destroy_worker+0x50/0x50 >> ret_from_fork+0x35/0x40 >> Modules linked in: >> ---[ end trace c2425e6e89b5558f ]--- >> >> [CAUSE] >> The offending csum tree looks like this: >> checksum tree key (CSUM_TREE ROOT_ITEM 0) >> node 29741056 level 1 items 14 free 107 generation 19 owner CSUM_TREE >> ... >> key (EXTENT_CSUM EXTENT_CSUM 85975040) block 29630464 gen 17 >> key (EXTENT_CSUM EXTENT_CSUM 89911296) block 29642752 gen 17 <<< >> key (EXTENT_CSUM EXTENT_CSUM 92274688) block 29646848 gen 17 >> ... >> >> leaf 29630464 items 6 free space 1 generation 17 owner CSUM_TREE >> item 0 key (EXTENT_CSUM EXTENT_CSUM 85975040) itemoff 3987 itemsize 8 >> range start 85975040 end 85983232 length 8192 >> ... >> leaf 29642752 items 0 free space 3995 generation 17 owner 0 >> ^ empty leaf invalid owner ^ >> >> leaf 29646848 items 1 free space 602 generation 17 owner CSUM_TREE >> item 0 key (EXTENT_CSUM EXTENT_CSUM 92274688) itemoff 627 itemsize 3368 >> range start 92274688 end 95723520 length 3448832 >> >> So we have a corrupted csum tree where one tree leaf is completely >> empty, causing unbalanced btree, thus leading to unexpected btree >> balance error. >> >> [FIX] >> For this particular case, we handle it in two directions to catch it: >> - Check if the tree block is empty through btrfs_verify_level_key() >> So that invalid tree blocks won't be read out through >> btrfs_search_slot() and its variants. >> >> - Check 0 tree owner in tree checker >> NO tree is using 0 as its tree owner, detect it and reject at tree >> block read time. >> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=202821 >> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> >> --- >> fs/btrfs/disk-io.c | 8 ++++++++ >> fs/btrfs/tree-checker.c | 6 ++++++ >> 2 files changed, 14 insertions(+) >> >> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c >> index deb74a8c191a..a843c21f3060 100644 >> --- a/fs/btrfs/disk-io.c >> +++ b/fs/btrfs/disk-io.c >> @@ -414,6 +414,14 @@ int btrfs_verify_level_key(struct extent_buffer *eb, int level, >> >> if (!first_key) >> return 0; >> + /* We have @first_key, so this @eb must have at least one item */ >> + if (btrfs_header_nritems(eb) == 0) { >> + btrfs_err(fs_info, >> + "invalid tree nritems, bytenr=%llu nritems=0 expect >0", >> + eb->start); >> + WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)); >> + return -EUCLEAN; >> + } > > Shouldn't this check be before !first_key, e.g. we always want to verify > that a particular node has at least 1 item ? Nope, it's possible that we have case like read csum tree root. In that case, we don't have first key, and csum tree can be empty. Thanks, Qu > >> >> /* >> * For live tree block (new tree blocks in current transaction), >> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c >> index 96fce4bef4e7..a4c7f7ed8490 100644 >> --- a/fs/btrfs/tree-checker.c >> +++ b/fs/btrfs/tree-checker.c >> @@ -888,6 +888,12 @@ static int check_leaf(struct extent_buffer *leaf, bool check_item_data) >> owner); >> return -EUCLEAN; >> } >> + /* Unknown tree */ >> + if (owner == 0) { >> + generic_err(leaf, 0, >> + "invalid owner, root 0 is not defined"); >> + return -EUCLEAN; >> + } >> return 0; >> } >> >>
