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    Subject[PATCH 5.4 08/46] staging: rtl8192e: fix potential use after free
    Date
    From: Pan Bian <bianpan2016@163.com>

    commit b7aa39a2ed0112d07fc277ebd24a08a7b2368ab9 upstream.

    The variable skb is released via kfree_skb() when the return value of
    _rtl92e_tx is not zero. However, after that, skb is accessed again to
    read its length, which may result in a use after free bug. This patch
    fixes the bug by moving the release operation to where skb is never
    used later.

    Signed-off-by: Pan Bian <bianpan2016@163.com>
    Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
    Cc: stable <stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/1572965351-6745-1-git-send-email-bianpan2016@163.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/staging/rtl8192e/rtl8192e/rtl_core.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
    +++ b/drivers/staging/rtl8192e/rtl8192e/rtl_core.c
    @@ -1616,14 +1616,15 @@ static void _rtl92e_hard_data_xmit(struc
    memcpy((unsigned char *)(skb->cb), &dev, sizeof(dev));
    skb_push(skb, priv->rtllib->tx_headroom);
    ret = _rtl92e_tx(dev, skb);
    - if (ret != 0)
    - kfree_skb(skb);

    if (queue_index != MGNT_QUEUE) {
    priv->rtllib->stats.tx_bytes += (skb->len -
    priv->rtllib->tx_headroom);
    priv->rtllib->stats.tx_packets++;
    }
    +
    + if (ret != 0)
    + kfree_skb(skb);
    }

    static int _rtl92e_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)

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