From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit fdafed459998e2be0e877e6189b24cb7a0183224 ]
GRE tunnel has its own header_ops, ipgre_header_ops, and sets it conditionally. When it is set, it assumes the outer IP header is already created before ipgre_xmit().
This is not true when we send packets through a raw packet socket, where L2 headers are supposed to be constructed by user. Packet socket calls dev_validate_header() to validate the header. But GRE tunnel does not set dev->hard_header_len, so that check can be simply bypassed, therefore uninit memory could be passed down to ipgre_xmit(). Similar for dev->needed_headroom.
dev->hard_header_len is supposed to be the length of the header created by dev->header_ops->create(), so it should be used whenever header_ops is set, and dev->needed_headroom should be used when it is not set.
Reported-and-tested-by: syzbot+4a2c52677a8a1aa283cb@syzkaller.appspotmail.com Cc: William Tu u9012063@gmail.com Acked-by: Willem de Bruijn willemb@google.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Xie He xie.he.0141@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/ip_gre.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index ffcb5983107db..de6f89511a216 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -680,9 +680,7 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb, }
if (dev->header_ops) { - /* Need space for new headers */ - if (skb_cow_head(skb, dev->needed_headroom - - (tunnel->hlen + sizeof(struct iphdr)))) + if (skb_cow_head(skb, 0)) goto free_skb;
tnl_params = (const struct iphdr *)skb->data; @@ -800,7 +798,11 @@ static void ipgre_link_update(struct net_device *dev, bool set_mtu) len = tunnel->tun_hlen - len; tunnel->hlen = tunnel->hlen + len;
- dev->needed_headroom = dev->needed_headroom + len; + if (dev->header_ops) + dev->hard_header_len += len; + else + dev->needed_headroom += len; + if (set_mtu) dev->mtu = max_t(int, dev->mtu - len, 68);
@@ -1003,6 +1005,7 @@ static void __gre_tunnel_init(struct net_device *dev) tunnel->parms.iph.protocol = IPPROTO_GRE;
tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen; + dev->needed_headroom = tunnel->hlen + sizeof(tunnel->parms.iph);
dev->features |= GRE_FEATURES; dev->hw_features |= GRE_FEATURES; @@ -1046,10 +1049,14 @@ static int ipgre_tunnel_init(struct net_device *dev) return -EINVAL; dev->flags = IFF_BROADCAST; dev->header_ops = &ipgre_header_ops; + dev->hard_header_len = tunnel->hlen + sizeof(*iph); + dev->needed_headroom = 0; } #endif } else if (!tunnel->collect_md) { dev->header_ops = &ipgre_header_ops; + dev->hard_header_len = tunnel->hlen + sizeof(*iph); + dev->needed_headroom = 0; }
return ip_tunnel_init(dev);