Commit 7f327080 authored by Taehee Yoo's avatar Taehee Yoo Committed by David S. Miller
Browse files

macsec: avoid to set wrong mtu

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

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

Fixes: c09440f7

 ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: default avatarTaehee Yoo <>
Signed-off-by: default avatarDavid S. Miller <>
parent c651b461
......@@ -4002,11 +4002,11 @@ static int macsec_newlink(struct net *net, struct net_device *dev,
struct netlink_ext_ack *extack)
struct macsec_dev *macsec = macsec_priv(dev);
rx_handler_func_t *rx_handler;
u8 icv_len = DEFAULT_ICV_LEN;
struct net_device *real_dev;
int err;
int err, mtu;
sci_t sci;
u8 icv_len = DEFAULT_ICV_LEN;
rx_handler_func_t *rx_handler;
if (!tb[IFLA_LINK])
return -EINVAL;
......@@ -4033,7 +4033,11 @@ 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;
dev->mtu = mtu;
rx_handler = rtnl_dereference(real_dev->rx_handler);
if (rx_handler && rx_handler != macsec_handle_frame)
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