Re: [PATCH] can: mcp251x: Fix resume from sleep before interface was brought up

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, May 04, 2021 at 06:01:48PM +0200, Schrempf Frieder wrote:
> Since 8ce8c0abcba3 the driver queues work via priv->restart_work when
> resuming after suspend, even when the interface was not previously
> enabled. This causes a null dereference error as the workqueue is
> only allocated and initialized in mcp251x_open().
> 
> To fix this we move the workqueue init to mcp251x_can_probe() as
> there is no reason to do it later and repeat it whenever
> mcp251x_open() is called.

AFAIU the IRQ is freed at ->ndo_stop() which is guaranteed to be called before
->remove(). If it's the case, we are fine.

FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Fixes: 8ce8c0abcba3 ("can: mcp251x: only reset hardware as required")
> Cc: stable@vger.kernel.org
> Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> ---
>  drivers/net/can/spi/mcp251x.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
> index a57da43680d8..42e8e5791c9f 100644
> --- a/drivers/net/can/spi/mcp251x.c
> +++ b/drivers/net/can/spi/mcp251x.c
> @@ -956,8 +956,6 @@ static int mcp251x_stop(struct net_device *net)
>  
>  	priv->force_quit = 1;
>  	free_irq(spi->irq, priv);
> -	destroy_workqueue(priv->wq);
> -	priv->wq = NULL;
>  
>  	mutex_lock(&priv->mcp_lock);
>  
> @@ -1224,15 +1222,6 @@ static int mcp251x_open(struct net_device *net)
>  		goto out_close;
>  	}
>  
> -	priv->wq = alloc_workqueue("mcp251x_wq", WQ_FREEZABLE | WQ_MEM_RECLAIM,
> -				   0);
> -	if (!priv->wq) {
> -		ret = -ENOMEM;
> -		goto out_clean;
> -	}
> -	INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);
> -	INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);
> -
>  	ret = mcp251x_hw_wake(spi);
>  	if (ret)
>  		goto out_free_wq;
> @@ -1373,6 +1362,15 @@ static int mcp251x_can_probe(struct spi_device *spi)
>  	if (ret)
>  		goto out_clk;
>  
> +	priv->wq = alloc_workqueue("mcp251x_wq", WQ_FREEZABLE | WQ_MEM_RECLAIM,
> +				   0);
> +	if (!priv->wq) {
> +		ret = -ENOMEM;
> +		goto out_clk;
> +	}
> +	INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);
> +	INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);
> +
>  	priv->spi = spi;
>  	mutex_init(&priv->mcp_lock);
>  
> @@ -1417,6 +1415,8 @@ static int mcp251x_can_probe(struct spi_device *spi)
>  	return 0;
>  
>  error_probe:
> +	destroy_workqueue(priv->wq);
> +	priv->wq = NULL;
>  	mcp251x_power_enable(priv->power, 0);
>  
>  out_clk:
> @@ -1438,6 +1438,9 @@ static int mcp251x_can_remove(struct spi_device *spi)
>  
>  	mcp251x_power_enable(priv->power, 0);
>  
> +	destroy_workqueue(priv->wq);
> +	priv->wq = NULL;
> +
>  	clk_disable_unprepare(priv->clk);
>  
>  	free_candev(net);
> -- 
> 2.25.1
> 
> 

-- 
With Best Regards,
Andy Shevchenko