netdev - [PATCH v2 net-next] net: dm9051: Fix use after free in dm9051_loop

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Date:   Mon, 21 Feb 2022 13:54:40 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Joseph CHAMG <josright123@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Joseph CHAMG <josright123@...il.com>, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH v2 net-next] net: dm9051: Fix use after free in
 dm9051_loop_tx()

This code dereferences "skb" after calling dev_kfree_skb().

Fixes: 2dc95a4d30ed ("net: Add dm9051 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
v2: Only record successful transfers

 drivers/net/ethernet/davicom/dm9051.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/davicom/dm9051.c b/drivers/net/ethernet/davicom/dm9051.c
index a63d17e669a0..20cdca06d267 100644
--- a/drivers/net/ethernet/davicom/dm9051.c
+++ b/drivers/net/ethernet/davicom/dm9051.c
@@ -845,17 +845,19 @@ static int dm9051_loop_tx(struct board_info *db)
 
 	while (!skb_queue_empty(&db->txq)) {
 		struct sk_buff *skb;
+		unsigned int len;
 
 		skb = skb_dequeue(&db->txq);
 		if (skb) {
 			ntx++;
 			ret = dm9051_single_tx(db, skb->data, skb->len);
+			len = skb->len;
 			dev_kfree_skb(skb);
 			if (ret < 0) {
 				db->bc.tx_err_counter++;
 				return 0;
 			}
-			ndev->stats.tx_bytes += skb->len;
+			ndev->stats.tx_bytes += len;
 			ndev->stats.tx_packets++;
 		}
 
-- 
2.20.1