gfs2: Fix slab-use-after-free in gfs2_qd_dealloc

In gfs2_put_super(), whether withdrawn or not, the quota should
be cleaned up by gfs2_quota_cleanup().

Otherwise, struct gfs2_sbd will be freed before gfs2_qd_dealloc (rcu
callback) has run for all gfs2_quota_data objects, resulting in
use-after-free.

Also, gfs2_destroy_threads() and gfs2_quota_cleanup() is already called
by gfs2_make_fs_ro(), so in gfs2_put_super(), after calling
gfs2_make_fs_ro(), there is no need to call them again.

Reported-by: syzbot+29c47e9e51895928698c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=29c47e9e51895928698c
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 726f062bc490aefc4a31f9c4ba08fa709734b856..84e88b50ed92c662cd4470084a25c9d656f567a0 100644 (file)
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -602,13 +602,15 @@ restart:
        }
        spin_unlock(&sdp->sd_jindex_spin);
 
-       if (!sb_rdonly(sb)) {
+       if (!sb_rdonly(sb))
                gfs2_make_fs_ro(sdp);
-       }
-       if (gfs2_withdrawn(sdp)) {
-               gfs2_destroy_threads(sdp);
+       else {
+               if (gfs2_withdrawn(sdp))
+                       gfs2_destroy_threads(sdp);
+
                gfs2_quota_cleanup(sdp);
        }
+
        WARN_ON(gfs2_withdrawing(sdp));
 
        /*  At this point, we're through modifying the disk  */