net: ll_temac: Fix TX BD buffer overwrite

Just as the initial check, we need to ensure num_frag+1 buffers available,
as that is the number of buffers we are going to use.

This fixes a buffer overflow, which might be seen during heavy network
load. Complete lockup of TEMAC was reproducible within about 10 minutes of
a particular load.

Fixes: 84823ff80f74 ("net: ll_temac: Fix race condition causing TX hang")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index 9797aa3..cc482ee 100644 (file)
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -861,7 +861,7 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                smp_mb();
 
                /* Space might have just been freed - check again */
-               if (temac_check_tx_bd_space(lp, num_frag))
+               if (temac_check_tx_bd_space(lp, num_frag + 1))
                        return NETDEV_TX_BUSY;
 
                netif_wake_queue(ndev);