ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv

When mounting ocfs2 and then remounting it as read-only, a
slab-use-after-free occurs after the user uses a syscall to
quota_getnextquota.  Specifically, sb_dqinfo(sb, type)->dqi_priv is the
dangling pointer.

During the remounting process, the pointer dqi_priv is freed but is never
set as null leaving it to be accessed.  Additionally, the read-only option
for remounting sets the DQUOT_SUSPENDED flag instead of setting the
DQUOT_USAGE_ENABLED flags.  Moreover, later in the process of getting the
next quota, the function ocfs2_get_next_id is called and only checks the
quota usage flags and not the quota suspended flags.

To fix this, I set dqi_priv to null when it is freed after remounting with
read-only and put a check for DQUOT_SUSPENDED in ocfs2_get_next_id.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20241218023924.22821-2-dennis.lamerice@gmail.com
Fixes: 8f9e8f5fcc05 ("ocfs2: Fix Q_GETNEXTQUOTA for filesystem without quotas")
Signed-off-by: Dennis Lam <dennis.lamerice@gmail.com>
Reported-by: syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com
Tested-by: syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6731d26f.050a0220.1fb99c.014b.GAE@google.com/T/
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index 2b0daced98ebb487e831d99ae1d7e19bd45e9cb1..3404e7a30c330cc08463bc997100ca643ba5d2c6 100644 (file)
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -893,7 +893,7 @@ static int ocfs2_get_next_id(struct super_block *sb, struct kqid *qid)
        int status = 0;
 
        trace_ocfs2_get_next_id(from_kqid(&init_user_ns, *qid), type);
-       if (!sb_has_quota_loaded(sb, type)) {
+       if (!sb_has_quota_active(sb, type)) {
                status = -ESRCH;
                goto out;
        }

diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
index 73d3367c533b8a212a65e73fa7f8fa979499e692..2956d888c1314598b917832b7d08046be508d5c0 100644 (file)
--- a/fs/ocfs2/quota_local.c
+++ b/fs/ocfs2/quota_local.c
@@ -867,6 +867,7 @@ out:
        brelse(oinfo->dqi_libh);
        brelse(oinfo->dqi_lqi_bh);
        kfree(oinfo);
+       info->dqi_priv = NULL;
        return status;
 }