From: Dave Chinner <dchinner@xxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_qm.c | 40 ++++++++++++++++++++++++++--------------
1 file changed, 26 insertions(+), 14 deletions(-)
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index e2c542f6dcd4..78ca52e55f03 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -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;
+
}
/*
--
2.39.2
