IB/core: Fix qp_sec use after free access

When security_ib_alloc_security fails, qp->qp_sec memory is freed.
However ib_destroy_qp still tries to access this memory which result
in kernel crash. So its initialized to NULL to avoid such access.

Fixes: d291f1a6 ("IB/core: Enforce PKey security on QPs")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/security.c

@@ -432,8 +432,10 @@ int ib_create_qp_security(struct ib_qp *qp, struct ib_device *dev)
 	atomic_set(&qp->qp_sec->error_list_count, 0);
 	init_completion(&qp->qp_sec->error_complete);
 	ret = security_ib_alloc_security(&qp->qp_sec->security);
-	if (ret)
+	if (ret) {
 		kfree(qp->qp_sec);
+		qp->qp_sec = NULL;
+	}
 
 	return ret;
 }