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: d291f1a65232 ("IB/core: Enforce PKey security on QPs")
Signed-off-by: Parav Pandit <[e-mail]>
Reviewed-by: Daniel Jurgens <[e-mail]>
Signed-off-by: Leon Romanovsky <[e-mail]>
Signed-off-by: Doug Ledford <[e-mail]>

drivers/infiniband/core/security.c

···
 	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;
 }