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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Robert Hancock <robert.hancock@calian.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.19 224/239] net: axienet: fix number of TX ring slots for available check
Date:   Mon, 24 Jan 2022 19:44:22 +0100
Message-Id: <20220124183950.232834013@linuxfoundation.org>
In-Reply-To: <20220124183943.102762895@linuxfoundation.org>
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From: Robert Hancock <robert.hancock@calian.com>

commit aba57a823d2985a2cc8c74a2535f3a88e68d9424 upstream.

The check for the number of available TX ring slots was off by 1 since a
slot is required for the skb header as well as each fragment. This could
result in overwriting a TX ring slot that was still in use.

Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -682,7 +682,7 @@ axienet_start_xmit(struct sk_buff *skb,
 	num_frag = skb_shinfo(skb)->nr_frags;
 	cur_p = &lp->tx_bd_v[lp->tx_bd_tail];
 
-	if (axienet_check_tx_bd_space(lp, num_frag)) {
+	if (axienet_check_tx_bd_space(lp, num_frag + 1)) {
 		if (netif_queue_stopped(ndev))
 			return NETDEV_TX_BUSY;
 
@@ -692,7 +692,7 @@ axienet_start_xmit(struct sk_buff *skb,
 		smp_mb();
 
 		/* Space might have just been freed - check again */
-		if (axienet_check_tx_bd_space(lp, num_frag))
+		if (axienet_check_tx_bd_space(lp, num_frag + 1))
 			return NETDEV_TX_BUSY;
 
 		netif_wake_queue(ndev);