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jfs: nlink overflow in jfs_rename

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If nlink is maximal for a directory (-1) and inside that directory you
perform a rename for some child directory (not moving from the parent),
then the nlink of the first directory is first incremented and later
decremented. Normally this is fine, but when nlink = -1 this causes a
wrap around to 0, and then drop_nlink issues a warning.

After applying the patch syzbot no longer issues any warnings. I also
ran some basic fs tests to look for any regressions.

Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Reported-by: syzbot+9131ddfd7870623b719f@syzkaller.appspotmail.com
Closes: https://syzbot.org/bug?extid=9131ddfd7870623b719f
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
This commit is contained in:
Jori Koolstra 2025-10-28 13:22:12 +01:00 • committed by Dave Kleikamp
parent 4a26e7032d
commit 9218dc26fd
1 changed files with 4 additions and 2 deletions
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6
fs/jfs/namei.c
View file

@ -1228,7 +1228,7 @@ static int jfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
jfs_err("jfs_rename: dtInsert returned -EIO");
goto out_tx;
}
if (S_ISDIR(old_ip->i_mode))
if (S_ISDIR(old_ip->i_mode) && old_dir != new_dir)
inc_nlink(new_dir);
}
/*
@ -1244,7 +1244,9 @@ static int jfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
goto out_tx;
}
if (S_ISDIR(old_ip->i_mode)) {
drop_nlink(old_dir);
if (new_ip || old_dir != new_dir)
drop_nlink(old_dir);
if (old_dir != new_dir) {
/*
* Change inode number of parent for moved directory