[PATCH] RDMA/rxe: Fix possible NULL pointer dereference

[Alex Dewar]

skb_clone() is called without checking if the returned pointer is NULL
before it is dereferenced. Fix by adding an additional error check.

Fixes: e7ec96fc7932 ("RDMA/rxe: Fix skb lifetime in rxe_rcv_mcast_pkt()")
Addresses-Coverity-ID: 1497804: Null pointer dereferences (NULL_RETURNS)
Signed-off-by: Alex Dewar <alex.dewa...@gmail.com>
---
 drivers/infiniband/sw/rxe/rxe_recv.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_recv.c 
b/drivers/infiniband/sw/rxe/rxe_recv.c
index 11f3daf20768..a65936e12f89 100644
--- a/drivers/infiniband/sw/rxe/rxe_recv.c
+++ b/drivers/infiniband/sw/rxe/rxe_recv.c
@@ -266,10 +266,13 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct 
sk_buff *skb)
                /* for all but the last qp create a new clone of the
                 * skb and pass to the qp.
                 */
-               if (mce->qp_list.next != &mcg->qp_list)
+               if (mce->qp_list.next != &mcg->qp_list) {
                        per_qp_skb = skb_clone(skb, GFP_ATOMIC);
-               else
+                       if (!per_qp_skb)
+                               goto err2;
+               } else {
                        per_qp_skb = skb;
+               }
 
                per_qp_pkt = SKB_TO_PKT(per_qp_skb);
                per_qp_pkt->qp = qp;
@@ -283,6 +286,10 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct 
sk_buff *skb)
 
        return;
 
+err2:
+       spin_unlock_bh(&mcg->mcg_lock);
+       rxe_drop_ref(mcg);      /* drop ref from rxe_pool_get_key. */
+
 err1:
        kfree_skb(skb);
 }
-- 
2.28.0