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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, Esben Haabendal <esben@geanix.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.12 163/178] net: ll_temac: Fix TX BD buffer overwrite
Date:   Mon, 21 Jun 2021 18:16:17 +0200
Message-Id: <20210621154928.300583932@linuxfoundation.org>
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From: Esben Haabendal <esben@geanix.com>

commit c364df2489b8ef2f5e3159b1dff1ff1fdb16040d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/xilinx/ll_temac_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -849,7 +849,7 @@ temac_start_xmit(struct sk_buff *skb, st
 		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);