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net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send
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[ Upstream commit 6d72e7c ]

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: b9b17de ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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Yunlongs authored and gregkh committed May 14, 2021
1 parent 0648941 commit e407495
Showing 1 changed file with 3 additions and 1 deletion.
4 changes: 3 additions & 1 deletion drivers/net/ethernet/qualcomm/emac/emac-mac.c
Original file line number Diff line number Diff line change
Expand Up @@ -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));

Expand All @@ -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,
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