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macvlan: enforce a consistent minimal mtu

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commit b64085b00044bdf3cd1c9825e9ef5b2e0feae91a upstream.

macvlan should enforce a minimal mtu of 68, even at link creation.

This patch avoids the current behavior (which could lead to crashes
in ipv6 stack if the link is brought up)

$ ip link add macvlan1 link eno1 mtu 8 type macvlan  # This should fail !
$ ip link sh dev macvlan1
5: macvlan1@eno1: <BROADCAST,MULTICAST> mtu 8 qdisc noop
    state DOWN mode DEFAULT group default qlen 1000
    link/ether 02:47:6c:24:74:82 brd ff:ff:ff:ff:ff:ff
$ ip link set macvlan1 mtu 67
Error: mtu less than device minimum.
$ ip link set macvlan1 mtu 68
$ ip link set macvlan1 mtu 8
Error: mtu less than device minimum.

Fixes: 91572088e3fd ("net: use core MTU range checking in core net infra")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2022-10-07 15:57:43 -07:00 committed by Greg Kroah-Hartman
parent 95ebea5a15
commit e929ec98c0
1 changed files with 1 additions and 1 deletions
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2
drivers/net/macvlan.c
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@ -1176,7 +1176,7 @@ void macvlan_common_setup(struct net_device *dev)
{
ether_setup(dev);
dev->min_mtu = 0;
/* ether_setup() has set dev->min_mtu to ETH_MIN_MTU. */
dev->max_mtu = ETH_MAX_MTU;
dev->priv_flags &= ~IFF_TX_SKB_SHARING;
netif_keep_dst(dev);