netdev - RE: [PATCH net v2] ravb: Fix races between ravb_tx_timeout

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Date: Tue, 14 Nov 2023 08:52:29 +0000
From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To: "s.shtylyov@....ru" <s.shtylyov@....ru>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH net v2] ravb: Fix races between ravb_tx_timeout_work() and
 net related ops

Hello,

> From: Yoshihiro Shimoda, Sent: Thursday, October 19, 2023 8:33 PM
> 
> Fix races between ravb_tx_timeout_work() and functions of net_device_ops
> and ethtool_ops by using rtnl_trylock() and rtnl_unlock(). Note that
> since ravb_close() is under the rtnl lock and calls cancel_work_sync(),
> ravb_tx_timeout_work() should calls rtnl_trylock(). Otherwise, a deadlock
> may happen in ravb_tx_timeout_work() like below:
> 
> CPU0			CPU1
> 			ravb_tx_timeout()
> 			schedule_work()
> ...
> __dev_close_many()
> // Under rtnl lock
> ravb_close()
> cancel_work_sync()
> // Waiting
> 			ravb_tx_timeout_work()
> 			rtnl_lock()
> 			// This is possible to cause a deadlock
> 
> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>

Gentle ping. I confirmed that I could apply this patch on
the latest net.git / main branch.

Best regards,
Yoshihiro Shimoda

> ---
> Changes from v1:
<snip URL>
>  - Modify commit description.
>  - Use goto in a error path.
> 
>  drivers/net/ethernet/renesas/ravb_main.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 0ef0b88b7145..300c1885e1e1 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1874,6 +1874,9 @@ static void ravb_tx_timeout_work(struct work_struct *work)
>  	struct net_device *ndev = priv->ndev;
>  	int error;
> 
> +	if (!rtnl_trylock())
> +		return;
> +
>  	netif_tx_stop_all_queues(ndev);
> 
>  	/* Stop PTP Clock driver */
> @@ -1907,7 +1910,7 @@ static void ravb_tx_timeout_work(struct work_struct *work)
>  		 */
>  		netdev_err(ndev, "%s: ravb_dmac_init() failed, error %d\n",
>  			   __func__, error);
> -		return;
> +		goto out_unlock;
>  	}
>  	ravb_emac_init(ndev);
> 
> @@ -1917,6 +1920,9 @@ static void ravb_tx_timeout_work(struct work_struct *work)
>  		ravb_ptp_init(ndev, priv->pdev);
> 
>  	netif_tx_start_all_queues(ndev);
> +
> +out_unlock:
> +	rtnl_unlock();
>  }
> 
>  /* Packet transmit function for Ethernet AVB */
> --
> 2.25.1