linux-kernel - [PATCH AUTOSEL 4.14 043/103] IB/ipoib: Ensure that MTU isn't less than minimum permitted

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Message-Id: <20191108114310.14363-43-sashal@kernel.org>
Date:   Fri,  8 Nov 2019 06:42:08 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Muhammad Sammar <muhammads@...lanox.com>,
        Feras Daoud <ferasda@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sasha Levin <sashal@...nel.org>, linux-rdma@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 043/103] IB/ipoib: Ensure that MTU isn't less than minimum permitted

From: Muhammad Sammar <muhammads@...lanox.com>

[ Upstream commit 142a9c287613560edf5a03c8d142c8b6ebc1995b ]

It is illegal to change MTU to a value lower than the minimum MTU
stated in ethernet spec. In addition to that we need to add 4 bytes
for encapsulation header (IPOIB_ENCAP_LEN).

Before "ifconfig ib0 mtu 0" command, succeeds while it obviously shouldn't.

Signed-off-by: Muhammad Sammar <muhammads@...lanox.com>
Reviewed-by: Feras Daoud <ferasda@...lanox.com>
Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/infiniband/ulp/ipoib/ipoib_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 1a93d3d58c8a4..caae4bfab950d 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -249,7 +249,8 @@ static int ipoib_change_mtu(struct net_device *dev, int new_mtu)
 		return 0;
 	}
 
-	if (new_mtu > IPOIB_UD_MTU(priv->max_ib_mtu))
+	if (new_mtu < (ETH_MIN_MTU + IPOIB_ENCAP_LEN) ||
+	    new_mtu > IPOIB_UD_MTU(priv->max_ib_mtu))
 		return -EINVAL;
 
 	priv->admin_mtu = new_mtu;
-- 
2.20.1