staging/lustre/ldlm: fix NULL pointer dereference

Pointer '*exp' returned from call to function 'class_conn2export'
at line 523 may be NULL and may be dereferenced at line 543.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/9323
ntel-bug-id: https://jira.hpdd.intel.com/browse/LU-4629
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_lib.c b/drivers/staging/lustre/lustre/ldlm/ldlm_lib.c
index 1a8c0d7..42f5f1e 100644
--- a/drivers/staging/lustre/lustre/ldlm/ldlm_lib.c
+++ b/drivers/staging/lustre/lustre/ldlm/ldlm_lib.c
@@ -514,7 +514,7 @@
 		LASSERT (imp->imp_state == LUSTRE_IMP_DISCON);
 		GOTO(out_ldlm, rc);
 	}
-	LASSERT((*exp)->exp_connection);
+	LASSERT(*exp != NULL && (*exp)->exp_connection);
 
 	if (data) {
 		LASSERTF((ocd->ocd_connect_flags & data->ocd_connect_flags) ==