linux-kernel - Re: [PATCH] acpi: watchdog: properly initialize resources

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Message-ID: <20170915223909.GA3420@roeck-us.net>
Date:   Fri, 15 Sep 2017 15:39:09 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Ryan Kennedy <ryan5544@...il.com>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi: watchdog: properly initialize resources

On Fri, Sep 15, 2017 at 09:55:18PM +0200, Arnd Bergmann wrote:
> We copy a local resource structure into a list, but only
> initialize some of its members, as pointed out by gcc-4.4:
> 
> drivers/acpi/acpi_watchdog.c: In function 'acpi_watchdog_init':
> drivers/acpi/acpi_watchdog.c:105: error: 'res.child' may be used uninitialized in this function
> drivers/acpi/acpi_watchdog.c:105: error: 'res.sibling' may be used uninitialized in this function
> drivers/acpi/acpi_watchdog.c:105: error: 'res.parent' may be used uninitialized in this function
> drivers/acpi/acpi_watchdog.c:105: error: 'res.desc' may be used uninitialized in this function
> drivers/acpi/acpi_watchdog.c:105: error: 'res.name' may be used uninitialized in this function
> 
> Newer compilers can presumably optimize the uninitialized access
> away entirely and don't warn at all, but rely on the kzalloc()
> to zero the structure first. This adds an explicit initialization
> to force consistent behavior.
> 
> Fixes: 058dfc767008 ("ACPI / watchdog: Add support for WDAT hardware watchdog")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  drivers/acpi/acpi_watchdog.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/acpi_watchdog.c b/drivers/acpi/acpi_watchdog.c
> index bf22c29d2517..11b113f8e367 100644
> --- a/drivers/acpi/acpi_watchdog.c
> +++ b/drivers/acpi/acpi_watchdog.c
> @@ -66,7 +66,7 @@ void __init acpi_watchdog_init(void)
>  	for (i = 0; i < wdat->entries; i++) {
>  		const struct acpi_generic_address *gas;
>  		struct resource_entry *rentry;
> -		struct resource res;
> +		struct resource res = {};
>  		bool found;
>  
>  		gas = &entries[i].register_region;
> -- 
> 2.9.0
>