linux-kernel - [PATCH 4.19 88/98] xfs: fix missing ILOCK unlock when xfs_setattr

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Date:   Tue, 27 Aug 2019 09:51:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, benjamin.moody@...il.com,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dave Chinner <dchinner@...hat.com>,
        Salvatore Bonaccorso <carnil@...ian.org>
Subject: [PATCH 4.19 88/98] xfs: fix missing ILOCK unlock when xfs_setattr_nonsize fails due to EDQUOT

From: Darrick J. Wong <darrick.wong@...cle.com>

commit 1fb254aa983bf190cfd685d40c64a480a9bafaee upstream.

Benjamin Moody reported to Debian that XFS partially wedges when a chgrp
fails on account of being out of disk quota.  I ran his reproducer
script:

# adduser dummy
# adduser dummy plugdev

# dd if=/dev/zero bs=1M count=100 of=test.img
# mkfs.xfs test.img
# mount -t xfs -o gquota test.img /mnt
# mkdir -p /mnt/dummy
# chown -c dummy /mnt/dummy
# xfs_quota -xc 'limit -g bsoft=100k bhard=100k plugdev' /mnt

(and then as user dummy)

$ dd if=/dev/urandom bs=1M count=50 of=/mnt/dummy/foo
$ chgrp plugdev /mnt/dummy/foo

and saw:

================================================
WARNING: lock held when returning to user space!
5.3.0-rc5 #rc5 Tainted: G        W
------------------------------------------------
chgrp/47006 is leaving the kernel with locks still held!
1 lock held by chgrp/47006:
 #0: 000000006664ea2d (&xfs_nondir_ilock_class){++++}, at: xfs_ilock+0xd2/0x290 [xfs]

...which is clearly caused by xfs_setattr_nonsize failing to unlock the
ILOCK after the xfs_qm_vop_chown_reserve call fails.  Add the missing
unlock.

Reported-by: benjamin.moody@...il.com
Fixes: 253f4911f297 ("xfs: better xfs_trans_alloc interface")
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Reviewed-by: Dave Chinner <dchinner@...hat.com>
Tested-by: Salvatore Bonaccorso <carnil@...ian.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/xfs/xfs_iops.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -803,6 +803,7 @@ xfs_setattr_nonsize(
 
 out_cancel:
 	xfs_trans_cancel(tp);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 out_dqrele:
 	xfs_qm_dqrele(udqp);
 	xfs_qm_dqrele(gdqp);