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

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Date:   Mon, 12 Oct 2020 17:52:30 +0100
From:   Alex Dewar <alex.dewar90@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Alex Dewar <alex.dewar90@...il.com>,
        Zhu Yanjun <yanjunz@...dia.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Bob Pearson <rpearsonhpe@...il.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] RDMA/rxe: Fix possible NULL pointer dereference

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.dewar90@...il.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