linux-kernel - [PATCH 4.9 10/27] stmmac: reset last TSO segment size after device open

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Date:   Fri, 15 Dec 2017 10:51:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lars Persson <larper@...s.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 10/27] stmmac: reset last TSO segment size after device open

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lars Persson <lars.persson@...s.com>

[ Upstream commit 45ab4b13e46325d00f4acdb365d406e941a15f81 ]

The mss variable tracks the last max segment size sent to the TSO
engine. We do not update the hardware as long as we receive skb:s with
the same value in gso_size.

During a network device down/up cycle (mapped to stmmac_release() and
stmmac_open() callbacks) we issue a reset to the hardware and it
forgets the setting for mss. However we did not zero out our mss
variable so the next transmission of a gso packet happens with an
undefined hardware setting.

This triggers a hang in the TSO engine and eventuelly the netdev
watchdog will bark.

Fixes: f748be531d70 ("stmmac: support new GMAC4")
Signed-off-by: Lars Persson <larper@...s.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1795,6 +1795,7 @@ static int stmmac_open(struct net_device

 	priv->dma_buf_sz = STMMAC_ALIGN(buf_sz);
 	priv->rx_copybreak = STMMAC_RX_COPYBREAK;
+	priv->mss = 0;

 	ret = alloc_dma_desc_resources(priv);
 	if (ret < 0) {