From: Julian Wiedmann <jwi@linux.ibm.com>
Date: Thu, 30 Jul 2020 17:01:20 +0200
Subject: s390/qeth: don't process empty bridge port events
Git-commit: 02472e28b9a45471c6d8729ff2c7422baa9be46a
Patch-mainline: v5.9-rc1
References: git-fixes

Discard events that don't contain any entries. This shouldn't happen,
but subsequent code relies on being able to use entry 0. So better
be safe than accessing garbage.

Fixes: b4d72c08b358 ("qeth: bridgeport support - basic control")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/s390/net/qeth_l2_main.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -1447,6 +1447,10 @@ static void qeth_bridge_state_change(str
 	int extrasize;
 
 	QETH_CARD_TEXT(card, 2, "brstchng");
+	if (qports->num_entries == 0) {
+		QETH_CARD_TEXT(card, 2, "BPempty");
+		return;
+	}
 	if (qports->entry_length != sizeof(struct qeth_sbp_port_entry)) {
 		QETH_CARD_TEXT_(card, 2, "BPsz%04x", qports->entry_length);
 		return;