[3.16.y-ckt stable] Patch "net: make skb_gso_segment error handling more robust" has been added to staging queue

[Luis Henriques]

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

    net: make skb_gso_segment error handling more robust

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt12.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 1be080b5a871c774e92b3759e92f69a7cc537eb6 Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw at strlen.de>
Date: Mon, 20 Oct 2014 13:49:17 +0200
Subject: net: make skb_gso_segment error handling more robust

commit 330966e501ffe282d7184fde4518d5e0c24bc7f8 upstream.

skb_gso_segment has three possible return values:
1. a pointer to the first segmented skb
2. an errno value (IS_ERR())
3. NULL.  This can happen when GSO is used for header verification.

However, several callers currently test IS_ERR instead of IS_ERR_OR_NULL
and would oops when NULL is returned.

Note that these call sites should never actually see such a NULL return
value; all callers mask out the GSO bits in the feature argument.

However, there have been issues with some protocol handlers erronously not
respecting the specified feature mask in some cases.

It is preferable to get 'have to turn off hw offloading, else slow' reports
rather than 'kernel crashes'.

Signed-off-by: Florian Westphal <fw at strlen.de>
Signed-off-by: David S. Miller <davem at davemloft.net>
Cc: Ben Hutchings <ben at decadent.org.uk>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv4/ip_output.c                 | 2 +-
 net/netfilter/nfnetlink_queue_core.c | 2 +-
 net/openvswitch/datapath.c           | 2 ++
 net/xfrm/xfrm_output.c               | 2 ++
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 0f3e713c5e75..fead914b09f6 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -231,7 +231,7 @@ static int ip_finish_output_gso(struct sk_buff *skb)
 	 */
 	features = netif_skb_features(skb);
 	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
-	if (IS_ERR(segs)) {
+	if (IS_ERR_OR_NULL(segs)) {
 		kfree_skb(skb);
 		return -ENOMEM;
 	}
diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 108120f216b1..5b169db2049a 100644
--- a/net/netfilter/nfnetlink_queue_core.c
+++ b/net/netfilter/nfnetlink_queue_core.c
@@ -665,7 +665,7 @@ nfqnl_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
 	 * returned by nf_queue.  For instance, callers rely on -ECANCELED to
 	 * mean 'ignore this hook'.
 	 */
-	if (IS_ERR(segs))
+	if (IS_ERR_OR_NULL(segs))
 		goto out_err;
 	queued = 0;
 	err = 0;
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 1e71adeca318..4e6176d9a6cd 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -330,6 +330,8 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 	segs = __skb_gso_segment(skb, NETIF_F_SG, false);
 	if (IS_ERR(segs))
 		return PTR_ERR(segs);
+	if (segs == NULL)
+		return -EINVAL;

 	/* Queue all of the segments. */
 	skb = segs;
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index c51e8f7b8653..e44f36057a2a 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -157,6 +157,8 @@ static int xfrm_output_gso(struct sk_buff *skb)
 	kfree_skb(skb);
 	if (IS_ERR(segs))
 		return PTR_ERR(segs);
+	if (segs == NULL)
+		return -EINVAL;

 	do {
 		struct sk_buff *nskb = segs->next;