net: ll_temac: Make sure to free skb when it is completely used

commit 6aa32217a9a446275440ee8724b1ecaf1838df47 upstream.

With the skb pointer piggy-backed on the TX BD, we have a simple and
efficient way to free the skb buffer when the frame has been transmitted.
But in order to avoid freeing the skb while there are still fragments from
the skb in use, we need to piggy-back on the TX BD of the skb, not the
first.

Without this, we are doing use-after-free on the DMA side, when the first
BD of a multi TX BD packet is seen as completed in xmit_done, and the
remaining BDs are still being processed.

Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index 5b8451c58aa4c37eefcf71c280148fa450fc3db1..d4b7e95a81ba962b559d29c23110586419977228 100644 (file)
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -873,7 +873,6 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                return NETDEV_TX_OK;
        }
        cur_p->phys = cpu_to_be32(skb_dma_addr);
-       ptr_to_txbd((void *)skb, cur_p);
 
        for (ii = 0; ii < num_frag; ii++) {
                if (++lp->tx_bd_tail >= TX_BD_NUM)
@@ -912,6 +911,11 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
        }
        cur_p->app0 |= cpu_to_be32(STS_CTRL_APP0_EOP);
 
+       /* Mark last fragment with skb address, so it can be consumed
+        * in temac_start_xmit_done()
+        */
+       ptr_to_txbd((void *)skb, cur_p);
+
        tail_p = lp->tx_bd_p + sizeof(*lp->tx_bd_v) * lp->tx_bd_tail;
        lp->tx_bd_tail++;
        if (lp->tx_bd_tail >= TX_BD_NUM)