[34-longterm 149/209] econet: Fix crash in aun_incoming().

[Paul Gortmaker]

From: David S. Miller <davem@xxxxxxxxxxxxx>

  =====================================================================
  | This is a commit scheduled for the next v2.6.34 longterm release. |
  | If you see a problem with using this for longterm, please comment.|
  =====================================================================

commit 4e085e76cbe558b79b54cbab772f61185879bc64 upstream

Unconditional use of skb->dev won't work here,
try to fetch the econet device via skb_dst()->dev
instead.

Suggested by Eric Dumazet.

Reported-by: Nelson Elhage <nelhage@xxxxxxxxxxx>
Tested-by: Nelson Elhage <nelhage@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 net/econet/af_econet.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/net/econet/af_econet.c b/net/econet/af_econet.c
index e40e6b0..728d389 100644
--- a/net/econet/af_econet.c
+++ b/net/econet/af_econet.c
@@ -847,9 +847,13 @@ static void aun_incoming(struct sk_buff *skb, struct aunhdr *ah, size_t len)
 {
 	struct iphdr *ip = ip_hdr(skb);
 	unsigned char stn = ntohl(ip->saddr) & 0xff;
+	struct dst_entry *dst = skb_dst(skb);
+	struct ec_device *edev = NULL;
 	struct sock *sk;
 	struct sk_buff *newskb;
-	struct ec_device *edev = skb->dev->ec_ptr;
+
+	if (dst)
+		edev = dst->dev->ec_ptr;
 
 	if (! edev)
 		goto bad;
-- 
1.7.4.4

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