ceph: quota: fix null pointer dereference in quota check

This patch fixes a possible null pointer dereference in
check_quota_exceeded, detected by the static checker smatch, with the
following warning:

   fs/ceph/quota.c:240 check_quota_exceeded()
    error: we previously assumed 'realm' could be null (see line 188)

Fixes: b7a2921765cf ("ceph: quota: support for ceph.quota.max_files")
Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: Luis Henriques <[email protected]>
Reviewed-by: "Yan, Zheng" <[email protected]>
Signed-off-by: Ilya Dryomov <[email protected]>

diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index 32d4f13784ba5da85e420a565297eff6b3bf132a..03f4d24db8fe009dc4384b83162979c34f11d1e0 100644 (file)
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -237,7 +237,8 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
                ceph_put_snap_realm(mdsc, realm);
                realm = next;
        }
-       ceph_put_snap_realm(mdsc, realm);
+       if (realm)
+               ceph_put_snap_realm(mdsc, realm);
        up_read(&mdsc->snap_rwsem);
 
        return exceeded;