From: Muhammad Sammar <muhammads@mellanox.com>
Date: Tue, 28 Aug 2018 11:45:30 +0000 (+0300)
Subject: IB/ipoib: Ensure that MTU isn't less than minimum permitted
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=e30fb85862cd4f4cde55b9212a73297446d652e4;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

IB/ipoib: Ensure that MTU isn't less than minimum permitted

[ 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@mellanox.com>
Reviewed-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 1a93d3d58c8a..caae4bfab950 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;