This is a note to let you know that I've just added the patch titled udp: only allow UFO for packets from SOCK_DGRAM sockets to the 3.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: udp-only-allow-ufo-for-packets-from-sock_dgram-sockets.patch and it can be found in the queue-3.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Wed Mar 11 11:37:09 CET 2015 From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= <mkubecek@xxxxxxx> Date: Mon, 2 Mar 2015 18:27:11 +0100 Subject: udp: only allow UFO for packets from SOCK_DGRAM sockets From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= <mkubecek@xxxxxxx> [ 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 <mkubecek@xxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/ip_output.c | 3 ++- net/ipv6/ip6_output.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -845,7 +845,8 @@ static int __ip_append_data(struct sock cork->length += length; if (((length > mtu) || (skb && skb_has_frags(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); --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1286,7 +1286,8 @@ int ip6_append_data(struct sock *sk, int if (((length > mtu) || (skb && skb_has_frags(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); Patches currently in stable-queue which might be from mkubecek@xxxxxxx are queue-3.10/udp-only-allow-ufo-for-packets-from-sock_dgram-sockets.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html