staging: gdm724x: fix use after free in gdm_lte_rx()

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@vger.kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220228074331.GA13685@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/gdm724x/gdm_lte.c b/drivers/staging/gdm724x/gdm_lte.c
index 493ed48..0d8d8fe 100644 (file)
--- a/drivers/staging/gdm724x/gdm_lte.c
+++ b/drivers/staging/gdm724x/gdm_lte.c
@@ -76,14 +76,15 @@ 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;