linux-kernel - Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe function is NULL

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Date:	Sat, 28 Nov 2015 18:34:47 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	martin.wilck@...fujitsu.com
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	tpmdd-devel@...ts.sourceforge.net, u.kleine-koenig@...gutronix.de
Subject: Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe
 function is NULL

On Thu, Nov 26, 2015 at 08:01:34PM +0100, martin.wilck@...fujitsu.com wrote:
> From: Martin Wilck <Martin.Wilck@...fujitsu.com>
> 
> Since b8b2c7d845d5, platform_drv_probe() is called for all platform
> devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
> platform_drv_probe() will return the error code from dev_pm_domain_attach().
> 
> This causes real_probe() to enter the "probe_failed" path and set
> dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
> success if both dev->bus->probe and drv->probe are missing.
> 
> This may cause a panic later. For example, inserting the tpm_tis
> driver with parameter "force=1" (i.e. registering tpm_tis as a platform
> driver) will panic in tpmm_chip_alloc() because dev->driver is NULL:
> 
>      chip->cdev.owner = chip->pdev->driver->owner;
> 
> This patch fixes this by returning success in platform_drv_probe() if
> "just" dev_pm_domain_attach() had failed. This restores the semantics
> of platform_device_register_XXX() if the associated platform driver has
> no "probe" function.
> 
> Fixes: b8b2c7d845d5 ("base/platform: assert that dev_pm_domain
> callbacks are called unconditionally")
> 
> Signed-off-by: Martin Wilck <Martin.Wilck@...fujitsu.com>

Acked-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

> ---
>  drivers/base/platform.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 1dd6d3b..c994e76 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -513,10 +513,14 @@ static int platform_drv_probe(struct device *_dev)
>  		return ret;
>  
>  	ret = dev_pm_domain_attach(_dev, true);
> -	if (ret != -EPROBE_DEFER && drv->probe) {
> -		ret = drv->probe(dev);
> -		if (ret)
> -			dev_pm_domain_detach(_dev, true);
> +	if (ret != -EPROBE_DEFER) {
> +		if (drv->probe) {
> +			ret = drv->probe(dev);
> +			if (ret)
> +				dev_pm_domain_detach(_dev, true);
> +		} else
> +			/* don't fail if just dev_pm_domain_attach failed */
> +			ret = 0;
>  	}
>  
>  	if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
> -- 
> 1.8.3.1
> 
> 

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