[PATCH net v2] net: stmmac: Disable Tx queues when reconfiguring the interface

From: Yannick Vignon <redacted>

The Tx queues were not disabled in situations where the driver needed to
stop the interface to apply a new configuration. This could result in a
kernel panic when doing any of the 3 following actions:
* reconfiguring the number of queues (ethtool -L)
* reconfiguring the size of the ring buffers (ethtool -G)
* installing/removing an XDP program (ip l set dev ethX xdp)

Prevent the panic by making sure netif_tx_disable is called when stopping
an interface.

Without this patch, the following kernel panic can be observed when doing
any of the actions above:

Unable to handle kernel paging request at virtual address ffff80001238d040
[....]
 Call trace:
  dwmac4_set_addr+0x8/0x10
  dev_hard_start_xmit+0xe4/0x1ac
  sch_direct_xmit+0xe8/0x39c
  __dev_queue_xmit+0x3ec/0xaf0
  dev_queue_xmit+0x14/0x20
[...]
[ end trace 0000000000000002 ]---

Fixes: 5fabb01207a2d ("net: stmmac: Add initial XDP support")
Fixes: aa042f60e4961 ("net: stmmac: Add support to Ethtool get/set ring parameters")
Fixes: 0366f7e06a6be ("net: stmmac: add ethtool support for get/set channels")
Signed-off-by: Yannick Vignon <redacted>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index f12097c8a485..748195697e5a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -3802,6 +3802,8 @@ int stmmac_release(struct net_device *dev)
 	struct stmmac_priv *priv = netdev_priv(dev);
 	u32 chan;
 
+	netif_tx_disable(dev);
+
 	if (device_may_wakeup(priv->device))
 		phylink_speed_down(priv->phylink, false);
 	/* Stop and disconnect the PHY */

-- 
2.25.1

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski [off-list ref]:

On Wed, 24 Nov 2021 16:47:31 +0100 you wrote:

From: Yannick Vignon <redacted>

The Tx queues were not disabled in situations where the driver needed to
stop the interface to apply a new configuration. This could result in a
kernel panic when doing any of the 3 following actions:
* reconfiguring the number of queues (ethtool -L)
* reconfiguring the size of the ring buffers (ethtool -G)
* installing/removing an XDP program (ip l set dev ethX xdp)

[...]

Here is the summary with links:
  - [net,v2] net: stmmac: Disable Tx queues when reconfiguring the interface
    https://git.kernel.org/netdev/net/c/b270bfe69736

You are awesome, thank you!
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