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macsec: avoid to set wrong mtu

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[ Upstream commit 7f32708036 ]

When a macsec interface is created, the mtu is calculated with the lower
interface's mtu value.
If the mtu of lower interface is lower than the length, which is needed
by macsec interface, macsec's mtu value will be overflowed.
So, if the lower interface's mtu is too low, macsec interface's mtu
should be set to 0.

Test commands:
    ip link add dummy0 mtu 10 type dummy
    ip link add macsec0 link dummy0 type macsec
    ip link show macsec0

Before:
    11: macsec0@dummy0: <BROADCAST,MULTICAST,M-DOWN> mtu 4294967274
After:
    11: macsec0@dummy0: <BROADCAST,MULTICAST,M-DOWN> mtu 0

Fixes: c09440f7dc ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Taehee Yoo
2020-04-23 13:40:47 +00:00
committed by Chris
parent 1272ae5953
commit 94fd149cea
1 changed files with 9 additions and 5 deletions
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14
drivers/net/macsec.c
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@@ -3209,11 +3209,11 @@ static int macsec_newlink(struct net *net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[])
{
struct macsec_dev *macsec = macsec_priv(dev);
struct net_device *real_dev;
int err;
sci_t sci;
u8 icv_len = DEFAULT_ICV_LEN;
rx_handler_func_t *rx_handler;
u8 icv_len = DEFAULT_ICV_LEN;
struct net_device *real_dev;
int err, mtu;
sci_t sci;
if (!tb[IFLA_LINK])
return -EINVAL;
@@ -3229,7 +3229,11 @@ static int macsec_newlink(struct net *net, struct net_device *dev,
if (data && data[IFLA_MACSEC_ICV_LEN])
icv_len = nla_get_u8(data[IFLA_MACSEC_ICV_LEN]);
dev->mtu = real_dev->mtu - icv_len - macsec_extra_len(true);
mtu = real_dev->mtu - icv_len - macsec_extra_len(true);
if (mtu < 0)
dev->mtu = 0;
else
dev->mtu = mtu;
rx_handler = rtnl_dereference(real_dev->rx_handler);
if (rx_handler && rx_handler != macsec_handle_frame)