From: Michal Kubeček Date: Mon, 2 Mar 2015 17:27:11 +0000 (+0100) Subject: udp: only allow UFO for packets from SOCK_DGRAM sockets X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=8a0cafc9a8131cc545dc9924aed38f7176ee4ad7;p=people%2Fiwj%2Flinux.git udp: only allow UFO for packets from SOCK_DGRAM sockets [ Upstream commit acf8dd0a9d0b9e4cdb597c2f74802f79c699e802 ] If an over-MTU UDP datagram is sent through a SOCK_RAW socket to a UFO-capable device, ip_ufo_append_data() sets skb->ip_summed to CHECKSUM_PARTIAL unconditionally as all GSO code assumes transport layer checksum is to be computed on segmentation. However, in this case, skb->csum_start and skb->csum_offset are never set as raw socket transmit path bypasses udp_send_skb() where they are usually set. As a result, driver may access invalid memory when trying to calculate the checksum and store the result (as observed in virtio_net driver). Moreover, the very idea of modifying the userspace provided UDP header is IMHO against raw socket semantics (I wasn't able to find a document clearly stating this or the opposite, though). And while allowing CHECKSUM_NONE in the UFO case would be more efficient, it would be a bit too intrusive change just to handle a corner case like this. Therefore disallowing UFO for packets from SOCK_DGRAM seems to be the best option. Signed-off-by: Michal Kubecek Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index dd637fc4b553..05686c47a289 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -843,7 +843,8 @@ static int __ip_append_data(struct sock *sk, cork->length += length; if (((length > mtu) || (skb && skb_is_gso(skb))) && (sk->sk_protocol == IPPROTO_UDP) && - (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) { + (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len && + (sk->sk_type == SOCK_DGRAM)) { err = ip_ufo_append_data(sk, queue, getfrag, from, length, hh_len, fragheaderlen, transhdrlen, maxfraglen, flags); diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 12f7ef0f243a..d7907ecf0b75 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1294,7 +1294,8 @@ emsgsize: if (((length > mtu) || (skb && skb_is_gso(skb))) && (sk->sk_protocol == IPPROTO_UDP) && - (rt->dst.dev->features & NETIF_F_UFO)) { + (rt->dst.dev->features & NETIF_F_UFO) && + (sk->sk_type == SOCK_DGRAM)) { err = ip6_ufo_append_data(sk, getfrag, from, length, hh_len, fragheaderlen, transhdrlen, mtu, flags, rt);