[ 3.5.y.z extended stable ] Patch "ipv6: udp packets following an UFO enqueued packet need also" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ipv6: udp packets following an UFO enqueued packet need also

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 0ad917fa7b9aa3c72dc29dc2bea28fdc2b7fe914 Mon Sep 17 00:00:00 2001
From: Hannes Frederic Sowa <hannes at stressinduktion.org>
Date: Sat, 21 Sep 2013 06:27:00 +0200
Subject: [PATCH] ipv6: udp packets following an UFO enqueued packet need also
 be handled by UFO

commit 2811ebac2521ceac84f2bdae402455baa6a7fb47 upstream.

In the following scenario the socket is corked:
If the first UDP packet is larger then the mtu we try to append it to the
write queue via ip6_ufo_append_data. A following packet, which is smaller
than the mtu would be appended to the already queued up gso-skb via
plain ip6_append_data. This causes random memory corruptions.

In ip6_ufo_append_data we also have to be careful to not queue up the
same skb multiple times. So setup the gso frame only when no first skb
is available.

This also fixes a shortcoming where we add the current packet's length to
cork->length but return early because of a packet > mtu with dontfrag set
(instead of sutracting it again).

Found with trinity.

Cc: YOSHIFUJI Hideaki <yoshfuji at linux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Reported-by: Dmitry Vyukov <dvyukov at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv6/ip6_output.c | 53 +++++++++++++++++++++------------------------------
 1 file changed, 22 insertions(+), 31 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 8fa50aa..d00f1ad 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1135,6 +1135,8 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 	 * udp datagram
 	 */
 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
+		struct frag_hdr fhdr;
+
 		skb = sock_alloc_send_skb(sk,
 			hh_len + fragheaderlen + transhdrlen + 20,
 			(flags & MSG_DONTWAIT), &err);
@@ -1155,12 +1157,6 @@ static inline int ip6_ufo_append_data(struct sock *sk,

 		skb->ip_summed = CHECKSUM_PARTIAL;
 		skb->csum = 0;
-	}
-
-	err = skb_append_datato_frags(sk,skb, getfrag, from,
-				      (length - transhdrlen));
-	if (!err) {
-		struct frag_hdr fhdr;

 		/* Specify the length of each IPv6 datagram fragment.
 		 * It has to be a multiple of 8.
@@ -1171,15 +1167,10 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 		ipv6_select_ident(&fhdr, rt);
 		skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
 		__skb_queue_tail(&sk->sk_write_queue, skb);
-
-		return 0;
 	}
-	/* There is not enough support do UPD LSO,
-	 * so follow normal path
-	 */
-	kfree_skb(skb);

-	return err;
+	return skb_append_datato_frags(sk, skb, getfrag, from,
+				       (length - transhdrlen));
 }

 static inline struct ipv6_opt_hdr *ip6_opt_dup(struct ipv6_opt_hdr *src,
@@ -1351,27 +1342,27 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 	 * --yoshfuji
 	 */

-	cork->length += length;
-	if (length > mtu) {
-		int proto = sk->sk_protocol;
-		if (dontfrag && (proto == IPPROTO_UDP || proto == IPPROTO_RAW)){
-			ipv6_local_rxpmtu(sk, fl6, mtu-exthdrlen);
-			return -EMSGSIZE;
-		}
-
-		if (proto == IPPROTO_UDP &&
-		    (rt->dst.dev->features & NETIF_F_UFO)) {
+	if ((length > mtu) && dontfrag && (sk->sk_protocol == IPPROTO_UDP ||
+					   sk->sk_protocol == IPPROTO_RAW)) {
+		ipv6_local_rxpmtu(sk, fl6, mtu-exthdrlen);
+		return -EMSGSIZE;
+	}

-			err = ip6_ufo_append_data(sk, getfrag, from, length,
-						  hh_len, fragheaderlen,
-						  transhdrlen, mtu, flags, rt);
-			if (err)
-				goto error;
-			return 0;
-		}
+	skb = skb_peek_tail(&sk->sk_write_queue);
+	cork->length += length;
+	if (((length > mtu) ||
+	     (skb && skb_is_gso(skb))) &&
+	    (sk->sk_protocol == IPPROTO_UDP) &&
+	    (rt->dst.dev->features & NETIF_F_UFO)) {
+		err = ip6_ufo_append_data(sk, getfrag, from, length,
+					  hh_len, fragheaderlen,
+					  transhdrlen, mtu, flags, rt);
+		if (err)
+			goto error;
+		return 0;
 	}

-	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
+	if (!skb)
 		goto alloc_new_skb;

 	while (length > 0) {
--
1.8.3.2