From: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Date: Tue, 16 Aug 2011 10:56:54 +0000 (+0000)
Subject: IPoIB: Fix possible NULL dereference in ipoib_start_xmit()
X-Git-Tag: MMI-PSA29.97-13-9~18541^2~1
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=22cfb0bf6721bb1f865f67bc21e3c36c272faf36;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

IPoIB: Fix possible NULL dereference in ipoib_start_xmit()

Fix a bug introduced in 69cce1d14049 ("net: Abstract dst->neighbour
accesses behind helpers.") where we might dereference skb_dst(skb)
even if it is NULL, which causes:

    [  240.944030] BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
    [  240.948007] IP: [<ffffffffa0366ce9>] ipoib_start_xmit+0x39/0x280 [ib_ipoib]
    [...]
    [  240.948007] Call Trace:
    [  240.948007]  <IRQ>
    [  240.948007]  [<ffffffff812cd5e0>] dev_hard_start_xmit+0x2a0/0x590
    [  240.948007]  [<ffffffff8131f680>] ? arp_create+0x70/0x200
    [  240.948007]  [<ffffffff812e8e1f>] sch_direct_xmit+0xef/0x1c0

Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=41212
Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Roland Dreier <roland@purestorage.com>
---

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 43f89ba0a908..fe89c4660d55 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -717,11 +717,13 @@ static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	struct ipoib_neigh *neigh;
-	struct neighbour *n;
+	struct neighbour *n = NULL;
 	unsigned long flags;
 
-	n = dst_get_neighbour(skb_dst(skb));
-	if (likely(skb_dst(skb) && n)) {
+	if (likely(skb_dst(skb)))
+		n = dst_get_neighbour(skb_dst(skb));
+
+	if (likely(n)) {
 		if (unlikely(!*to_ipoib_neigh(n))) {
 			ipoib_path_lookup(skb, dev);
 			return NETDEV_TX_OK;