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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Julian Wiedmann <jwi@linux.ibm.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.4 17/62] s390/qeth: fix L2 header access in qeth_l3_osa_features_check()
Date:   Fri, 15 Jan 2021 13:27:39 +0100
Message-Id: <20210115121959.239459241@linuxfoundation.org>
In-Reply-To: <20210115121958.391610178@linuxfoundation.org>
References: <20210115121958.391610178@linuxfoundation.org>
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From: Julian Wiedmann <jwi@linux.ibm.com>

[ Upstream commit f9c4845385c8f6631ebd5dddfb019ea7a285fba4 ]

ip_finish_output_gso() may call .ndo_features_check() even before the
skb has a L2 header. This conflicts with qeth_get_ip_version()'s attempt
to inspect the L2 header via vlan_eth_hdr().

Switch to vlan_get_protocol(), as already used further down in the
common qeth_features_check() path.

Fixes: f13ade199391 ("s390/qeth: run non-offload L3 traffic over common xmit path")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/s390/net/qeth_l3_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2114,7 +2114,7 @@ static netdev_features_t qeth_l3_osa_fea
 						    struct net_device *dev,
 						    netdev_features_t features)
 {
-	if (qeth_get_ip_version(skb) != 4)
+	if (vlan_get_protocol(skb) != htons(ETH_P_IP))
 		features &= ~NETIF_F_HW_VLAN_CTAG_TX;
 	return qeth_features_check(skb, dev, features);
 }