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xfs: quotacheck failure can race with background inode inactivation

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The background inode inactivation can attached dquots to inodes, but
this can race with a foreground quotacheck failure that leads to
disabling quotas and freeing the mp->m_quotainfo structure. The
background inode inactivation then tries to allocate a quota, tries
to dereference mp->m_quotainfo, and crashes like so:

XFS (loop1): Quotacheck: Unsuccessful (Error -5): Disabling quotas.
xfs filesystem being mounted at /root/syzkaller.qCVHXV/0/file0 supports timestamps until 2038 (0x7fffffff)
BUG: kernel NULL pointer dereference, address: 00000000000002a8
....
CPU: 0 PID: 161 Comm: kworker/0:4 Not tainted 6.2.0-c9c3395d5e3d #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Workqueue: xfs-inodegc/loop1 xfs_inodegc_worker
RIP: 0010:xfs_dquot_alloc+0x95/0x1e0
....
Call Trace:
 <TASK>
 xfs_qm_dqread+0x46/0x440
 xfs_qm_dqget_inode+0x154/0x500
 xfs_qm_dqattach_one+0x142/0x3c0
 xfs_qm_dqattach_locked+0x14a/0x170
 xfs_qm_dqattach+0x52/0x80
 xfs_inactive+0x186/0x340
 xfs_inodegc_worker+0xd3/0x430
 process_one_work+0x3b1/0x960
 worker_thread+0x52/0x660
 kthread+0x161/0x1a0
 ret_from_fork+0x29/0x50
 </TASK>
....

Prevent this race by flushing all the queued background inode
inactivations pending before purging all the cached dquots when
quotacheck fails.

Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Dave Chinner 2023-03-05 15:13:22 -08:00 committed by Darrick J. Wong
parent fe15c26ee2
commit 0c7273e494
1 changed files with 26 additions and 14 deletions
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40
fs/xfs/xfs_qm.c
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@ -1321,15 +1321,14 @@ xfs_qm_quotacheck(
error = xfs_iwalk_threaded(mp, 0, 0, xfs_qm_dqusage_adjust, 0, true,
NULL);
if (error) {
/*
* The inode walk may have partially populated the dquot
* caches. We must purge them before disabling quota and
* tearing down the quotainfo, or else the dquots will leak.
*/
xfs_qm_dqpurge_all(mp);
goto error_return;
}
/*
* On error, the inode walk may have partially populated the dquot
* caches. We must purge them before disabling quota and tearing down
* the quotainfo, or else the dquots will leak.
*/
if (error)
goto error_purge;
/*
* We've made all the changes that we need to make incore. Flush them
@ -1363,10 +1362,8 @@ xfs_qm_quotacheck(
* and turn quotaoff. The dquots won't be attached to any of the inodes
* at this point (because we intentionally didn't in dqget_noattach).
*/
if (error) {
xfs_qm_dqpurge_all(mp);
goto error_return;
}
if (error)
goto error_purge;
/*
* If one type of quotas is off, then it will lose its
@ -1376,7 +1373,7 @@ xfs_qm_quotacheck(
mp->m_qflags &= ~XFS_ALL_QUOTA_CHKD;
mp->m_qflags |= flags;
error_return:
error_return:
xfs_buf_delwri_cancel(&buffer_list);
if (error) {
@ -1395,6 +1392,21 @@ xfs_qm_quotacheck(
} else
xfs_notice(mp, "Quotacheck: Done.");
return error;
error_purge:
/*
* On error, we may have inodes queued for inactivation. This may try
* to attach dquots to the inode before running cleanup operations on
* the inode and this can race with the xfs_qm_destroy_quotainfo() call
* below that frees mp->m_quotainfo. To avoid this race, flush all the
* pending inodegc operations before we purge the dquots from memory,
* ensuring that background inactivation is idle whilst we turn off
* quotas.
*/
xfs_inodegc_flush(mp);
xfs_qm_dqpurge_all(mp);
goto error_return;
}
/*