nilfs2: enhance btree node keys check

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syzbot reported a warning on nilfs_btree_assign:
WARNING: fs/nilfs2/btree.c:2302 at nilfs_btree_assign+0x983/0xbe0 fs/nilfs2/btree.c:2302,

Analysis found that a corrupted file has the following btree layout:
Level2(key/ptr): [ 256/15 ]
Level1(key/ptr): [ 0/8, 1/9, 0/10, 3/11, 4/12, 5/13, 6/14,
                   139637976727559/16, 0/17 ]

The test truncated the file to 2 bytes, which partially zeroes the first
block and adds the file to the dirty list. When the segment constructor
writes it and assigns a new blocknr for the index block, it searches the
btree with key=0 and min level=2, and apparently returns -ENOENT.

Therefore, we should perform more checks on the btree nodes and return
early.

[ryusuke: split long lines in btree.c to satisfy checkpatch and
 improved the error message format for clarity]

Reported-by: syzbot+158be45e4d99232e1900@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=158be45e4d99232e1900
Signed-off-by: Wang Jianjian <wangjianjian3@huawei.com>
Fixes: 17c76b0104 ("nilfs2: B-tree based block mapping")
Cc: stable+noautosel@kernel.org # Warning suppression primarily
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

...

This commit is contained in:

Wang Jianjian 2026-08-10 23:20:52 +09:00 • committed by Viacheslav Dubeyko

parent 6b38b82be4

commit d7d54599a1

1 changed files with 16 additions and 3 deletions

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fs/nilfs2/btree.c

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