From b64085b00044bdf3cd1c9825e9ef5b2e0feae91a Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 7 Oct 2022 15:57:43 -0700
Subject: [PATCH] macvlan: enforce a consistent minimal mtu
Git-commit: b64085b00044bdf3cd1c9825e9ef5b2e0feae91a
Patch-mainline: v6.1-rc1
References: git-fixes
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
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/macvlan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 713e3354cb2e..8f8f73099de8 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -1192,7 +1192,7 @@ 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);
--
2.35.3