linux-kernel - [PATCH 4.14 07/78] ibmveth: Fix max MTU limit

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Message-Id: <20200629153806.2494953-8-sashal@kernel.org>
Date:   Mon, 29 Jun 2020 11:36:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Thomas Falcon <tlfalcon@...ux.ibm.com>,
        "David S . Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 4.14 07/78] ibmveth: Fix max MTU limit

From: Thomas Falcon <tlfalcon@...ux.ibm.com>

[ Upstream commit 5948378b26d89f8aa5eac37629dbd0616ce8d7a7 ]

The max MTU limit defined for ibmveth is not accounting for
virtual ethernet buffer overhead, which is twenty-two additional
bytes set aside for the ethernet header and eight additional bytes
of an opaque handle reserved for use by the hypervisor. Update the
max MTU to reflect this overhead.

Fixes: d894be57ca92 ("ethernet: use net core MTU range checking in more drivers")
Fixes: 110447f8269a ("ethernet: fix min/max MTU typos")
Signed-off-by: Thomas Falcon <tlfalcon@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/ibm/ibmveth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 880d925438c17..b43aebfc7f5be 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -1695,7 +1695,7 @@ static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
 	}
 
 	netdev->min_mtu = IBMVETH_MIN_MTU;
-	netdev->max_mtu = ETH_MAX_MTU;
+	netdev->max_mtu = ETH_MAX_MTU - IBMVETH_BUFF_OH;
 
 	memcpy(netdev->dev_addr, mac_addr_p, ETH_ALEN);
 
-- 
2.25.1