linux-kernel - Re: [PATCH v1 2/2] device property: Don't clear secondary pointer for shared primary firmware node

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Message-ID: <20201023123544.GB614478@kuha.fi.intel.com>
Date:   Fri, 23 Oct 2020 15:35:44 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Saravana Kannan <saravanak@...gle.com>,
        linux-acpi@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH v1 2/2] device property: Don't clear secondary pointer
 for shared primary firmware node

On Thu, Oct 22, 2020 at 09:41:00PM +0300, Andy Shevchenko wrote:
> It appears that firmware nodes can be shared between devices. In such case
> when a (child) device is about to be deleted, its firmware node may be shared
> and ACPI_COMPANION_SET(..., NULL) call for it breaks the secondary link
> of the shared primary firmware node.
> 
> In order to prevent that, check, if the device has a parent and parent's
> firmware node is shared with its child, and avoid crashing the link.
> 
> Fixes: c15e1bdda436 ("device property: Fix the secondary firmware node handling in set_primary_fwnode()")
> Reported-by: Ferry Toth <fntoth@...il.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/base/core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 41feab679fa1..78114ddac755 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4264,6 +4264,7 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
>   */
>  void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  {
> +	struct device *parent = dev->parent;
>  	struct fwnode_handle *fn = dev->fwnode;
>  
>  	if (fwnode) {
> @@ -4278,7 +4279,8 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  	} else {
>  		if (fwnode_is_primary(fn)) {
>  			dev->fwnode = fn->secondary;
> -			fn->secondary = ERR_PTR(-ENODEV);
> +			if (!(parent && fn == parent->fwnode))
> +				fn->secondary = ERR_PTR(-ENODEV);
>  		} else {
>  			dev->fwnode = NULL;
>  		}
> -- 
> 2.28.0

-- 
heikki