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From:   Lv Yunlong <lyl2019@mail.ustc.edu.cn>
To:     skashyap@marvell.com, jhasan@marvell.com,
        GR-QLogic-Storage-Upstream@marvell.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com, mlombard@redhat.com
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Subject: [PATCH] scsi/bnx2fc/bnx2fx_fcore: Fix a double free in bnx2fc_rcv
Date:   Mon, 24 May 2021 03:23:20 -0700
Message-Id: <20210524102320.10122-1-lyl2019@mail.ustc.edu.cn>
MIME-Version: 1.0
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Precedence: bulk

In bnx2fc_rcv, it calls skb_share_check(skb,GFP_ATOMIC) to clone
the skb. But if skb_clone() failed, skb_share_check() will free
the skb in the first time and return NULL. Then skb_share_check()
returns NULL and goto err.

Unfortunately, the same skb is freed in the second time in the err.

As kfree_skb() free a null pointer is a safe operation, my patch
put "skb = tmp_skb;" ahead of the "if(!tmp_skb) goto err;". So that
if skb_share_check() failed, skb will be a null pointer.

Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
index 8863a74e6c57..89c277cb93b2 100644
--- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
+++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
@@ -445,11 +445,10 @@ static int bnx2fc_rcv(struct sk_buff *skb, struct net_device *dev,
 	}
 
 	tmp_skb = skb_share_check(skb, GFP_ATOMIC);
+	skb = tmp_skb;
 	if (!tmp_skb)
 		goto err;
 
-	skb = tmp_skb;
-
 	if (unlikely(eth_hdr(skb)->h_proto != htons(ETH_P_FCOE))) {
 		printk(KERN_ERR PFX "bnx2fc_rcv: Wrong FC type frame\n");
 		goto err;
-- 
2.25.1