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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 5.15 796/846] net: axienet: Fix TX ring slot available check
Date:   Mon, 24 Jan 2022 19:45:13 +0100
Message-Id: <20220124184128.409686443@linuxfoundation.org>
In-Reply-To: <20220124184100.867127425@linuxfoundation.org>
References: <20220124184100.867127425@linuxfoundation.org>
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From: Robert Hancock <robert.hancock@calian.com>

commit 996defd7f8b5dafc1d480b7585c7c62437f80c3c upstream.

The check for whether a TX ring slot was available was incorrect,
since a slot which had been loaded with transmit data but the device had
not started transmitting would be treated as available, potentially
causing non-transmitted slots to be overwritten. The control field in
the descriptor should be checked, rather than the status field (which may
only be updated when the device completes the entry).

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
@@ -643,7 +643,6 @@ static int axienet_free_tx_chain(struct
 		if (cur_p->skb && (status & XAXIDMA_BD_STS_COMPLETE_MASK))
 			dev_consume_skb_irq(cur_p->skb);
 
-		cur_p->cntrl = 0;
 		cur_p->app0 = 0;
 		cur_p->app1 = 0;
 		cur_p->app2 = 0;
@@ -651,6 +650,7 @@ static int axienet_free_tx_chain(struct
 		cur_p->skb = NULL;
 		/* ensure our transmit path and device don't prematurely see status cleared */
 		wmb();
+		cur_p->cntrl = 0;
 		cur_p->status = 0;
 
 		if (sizep)
@@ -713,7 +713,7 @@ static inline int axienet_check_tx_bd_sp
 	/* Ensure we see all descriptor updates from device or TX IRQ path */
 	rmb();
 	cur_p = &lp->tx_bd_v[(lp->tx_bd_tail + num_frag) % lp->tx_bd_num];
-	if (cur_p->status & XAXIDMA_BD_STS_ALL_MASK)
+	if (cur_p->cntrl)
 		return NETDEV_TX_BUSY;
 	return 0;
 }