net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

In emac_mac_tx_buf_send, it calls emac_tx_fill_tpd(..,skb,..).
If some error happens in emac_tx_fill_tpd(), the skb will be freed via
dev_kfree_skb(skb) in error branch of emac_tx_fill_tpd().
But the freed skb is still used via skb->len by netdev_sent_queue(,skb->len).

As i observed that emac_tx_fill_tpd() haven't modified the value of skb->len,
thus my patch assigns skb->len to 'len' before the possible free and
use 'len' instead of skb->len later.

Fixes: b9b17debc69d2 ("net: emac: emac gigabit ethernet controller driver")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/qualcomm/emac/emac-mac.c b/drivers/net/ethernet/qualcomm/emac/emac-mac.c
index 117188e..87b8c03 100644 (file)
--- a/drivers/net/ethernet/qualcomm/emac/emac-mac.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac-mac.c
@@ -1437,6 +1437,7 @@ netdev_tx_t emac_mac_tx_buf_send(struct emac_adapter *adpt,
 {
        struct emac_tpd tpd;
        u32 prod_idx;
+       int len;
 
        memset(&tpd, 0, sizeof(tpd));
 
@@ -1456,9 +1457,10 @@ netdev_tx_t emac_mac_tx_buf_send(struct emac_adapter *adpt,
        if (skb_network_offset(skb) != ETH_HLEN)
                TPD_TYP_SET(&tpd, 1);
 
+       len = skb->len;
        emac_tx_fill_tpd(adpt, tx_q, skb, &tpd);
 
-       netdev_sent_queue(adpt->netdev, skb->len);
+       netdev_sent_queue(adpt->netdev, len);
 
        /* Make sure the are enough free descriptors to hold one
         * maximum-sized SKB.  We need one desc for each fragment,