From: Hangbin Liu liuhangbin@gmail.com
[ Upstream commit e2c693934194fd3b4e795635934883354c06ebc9 ]
In __icmp_send() there is a possibility that the rt->dst.dev is NULL, e,g, with tunnel collect_md mode, which will cause kernel crash. Here is what the code path looks like, for GRE:
- ip6gre_tunnel_xmit - ip6gre_xmit_ipv4 - __gre6_xmit - ip6_tnl_xmit - if skb->len - t->tun_hlen - eth_hlen > mtu; return -EMSGSIZE - icmp_send - net = dev_net(rt->dst.dev); <-- here
The reason is __metadata_dst_init() init dst->dev to NULL by default. We could not fix it in __metadata_dst_init() as there is no dev supplied. On the other hand, the reason we need rt->dst.dev is to get the net. So we can just try get it from skb->dev when rt->dst.dev is NULL.
v4: Julian Anastasov remind skb->dev also could be NULL. We'd better still use dst.dev and do a check to avoid crash.
v3: No changes.
v2: fix the issue in __icmp_send() instead of updating shared dst dev in {ip_md, ip6}_tunnel_xmit.
Fixes: c8b34e680a09 ("ip_tunnel: Add tnl_update_pmtu in ip_md_tunnel_xmit") Signed-off-by: Hangbin Liu liuhangbin@gmail.com Reviewed-by: Julian Anastasov ja@ssi.bg Acked-by: Jonathan Lemon jonathan.lemon@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/icmp.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -587,7 +587,13 @@ void __icmp_send(struct sk_buff *skb_in,
if (!rt) goto out; - net = dev_net(rt->dst.dev); + + if (rt->dst.dev) + net = dev_net(rt->dst.dev); + else if (skb_in->dev) + net = dev_net(skb_in->dev); + else + goto out;
/* * Find the original header. It is expected to be valid, of course.