[ Upstream commit
c780a049f9bf442314335372c9abc4548bfe3e44 ]
While working on yet another syzkaller report, I found
that our IP_MAX_MTU enforcements were not properly done.
gcc seems to reload dev->mtu for min(dev->mtu, IP_MAX_MTU), and
final result can be bigger than IP_MAX_MTU :/
This is a problem because device mtu can be changed on other cpus or
threads.
While this patch does not fix the issue I am working on, it is
probably worth addressing it.
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>
!forwarding)
return dst_mtu(dst);
- return min(dst->dev->mtu, IP_MAX_MTU);
+ return min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
}
static inline unsigned int ip_skb_dst_mtu(struct sock *sk,
return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding);
}
- return min(skb_dst(skb)->dev->mtu, IP_MAX_MTU);
+ return min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU);
}
u32 ip_idents_reserve(u32 hash, int segs);
if (mtu)
return mtu;
- mtu = dst->dev->mtu;
+ mtu = READ_ONCE(dst->dev->mtu);
if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
if (rt->rt_uses_gateway && mtu > 576)