Commit 9218dc26 authored by Jori Koolstra's avatar Jori Koolstra Committed by Dave Kleikamp
Browse files

jfs: nlink overflow in jfs_rename 



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: default avatarJori Koolstra <jkoolstra@xs4all.nl>
Reported-by: default avatar <syzbot+9131ddfd7870623b719f@syzkaller.appspotmail.com>
Closes: https://syzbot.org/bug?extid=9131ddfd7870623b719f


Signed-off-by: default avatarDave Kleikamp <dave.kleikamp@oracle.com>
parent 4a26e703

fs/jfs/namei.c

+4 −2
Original line number Diff line number Diff line
@@ -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)) {

		if (new_ip || old_dir != new_dir)

			drop_nlink(old_dir);



		if (old_dir != new_dir) {

			/*

			 * Change inode number of parent for moved directory