linux-kernel - [PATCH 4.14 17/23] staging: gdm724x: fix use after free in gdm_lte

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Message-Id: <20220314112731.556800270@linuxfoundation.org>
Date:   Mon, 14 Mar 2022 12:34:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH 4.14 17/23] staging: gdm724x: fix use after free in gdm_lte_rx()

From: Dan Carpenter <dan.carpenter@...cle.com>

commit fc7f750dc9d102c1ed7bbe4591f991e770c99033 upstream.

The netif_rx_ni() function frees the skb so we can't dereference it to
save the skb->len.

Fixes: 61e121047645 ("staging: gdm7240: adding LTE USB driver")
Cc: stable <stable@...r.kernel.org>
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Link: https://lore.kernel.org/r/20220228074331.GA13685@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/staging/gdm724x/gdm_lte.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/staging/gdm724x/gdm_lte.c
+++ b/drivers/staging/gdm724x/gdm_lte.c
@@ -85,14 +85,15 @@ static void tx_complete(void *arg)
 
 static int gdm_lte_rx(struct sk_buff *skb, struct nic *nic, int nic_type)
 {
-	int ret;
+	int ret, len;
 
+	len = skb->len + ETH_HLEN;
 	ret = netif_rx_ni(skb);
 	if (ret == NET_RX_DROP) {
 		nic->stats.rx_dropped++;
 	} else {
 		nic->stats.rx_packets++;
-		nic->stats.rx_bytes += skb->len + ETH_HLEN;
+		nic->stats.rx_bytes += len;
 	}
 
 	return 0;