[PATCH] gfs2: Fix slab-use-after-free in gfs2_qd_dispose
Deepanshu Kartikey <[email protected]>
| Newsgroups | dev.linux.lists.gfs2,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
In gfs2_qd_dispose(), the quota data (qd) is removed from qd_list and
qd_hlist, but not removed from the LRU list before call_rcu() is
invoked to free the object.
This can lead to a use-after-free when the shrinker (gfs2_qd_shrink_scan)
runs concurrently with filesystem unmount. The shrinker attempts to walk
the LRU list via list_lru_shrink_walk(), accessing quota data that has
already been freed by the RCU callback (gfs2_qd_dealloc).
Fix this by calling list_lru_del_obj() to remove the quota data from
the LRU list before scheduling the RCU callback.
Fixes: faada74a90563 ("gfs2: Factor out duplicate quota data disposal code")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=046b605f01802054bff0
Signed-off-by: Deepanshu Kartikey <[email protected]>
---
Note: Only compile-tested. No reproducer available from syzbot.
---
fs/gfs2/quota.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index b1692f12a602..85b0b5105b4b 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -125,6 +125,8 @@ static void gfs2_qd_dispose(struct gfs2_quota_data *qd)
hlist_bl_del_rcu(&qd->qd_hlist);
spin_unlock_bucket(qd->qd_hash);
+ list_lru_del_obj(&gfs2_qd_lru, &qd->qd_lru);
+
if (!gfs2_withdrawn(sdp)) {
gfs2_assert_warn(sdp, !qd->qd_change);
gfs2_assert_warn(sdp, !qd->qd_slot_ref);
--
2.43.0