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

Sasha Levin
2019-11-08T11:59:30Z

From: Muhammad Sammar <muhammads@mellanox.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@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>
---
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