linux-kernel - Re: [PATCH 3/4] dell-laptop: Fix allocating & freeing SMI buffer page

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Date:	Mon, 22 Jun 2015 10:46:01 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Darren Hart <dvhart@...radead.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 3/4] dell-laptop: Fix allocating & freeing SMI buffer page

On Sun 21-06-15 10:41:03, Pali Rohár wrote:
> This commit fix kernel crash when probing for rfkill devices in dell-laptop
> driver failed. Function free_page() was incorrectly used on struct page *
> instead of virtual address of SMI buffer.
> 
> This commit also simplify allocating page for SMI buffer by using
> __get_free_page() function instead of sequential call of functions
> alloc_page() and page_address().
> 
> Signed-off-by: Pali Rohár <pali.rohar@...il.com>

Looks good to me.
FWIW
Acked-by: Michal Hocko <mhocko@...e.cz>

> ---
>  drivers/platform/x86/dell-laptop.c |    8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> index aaef335..0a91599 100644
> --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -306,7 +306,6 @@ static const struct dmi_system_id dell_quirks[] __initconst = {
>  };
>  
>  static struct calling_interface_buffer *buffer;
> -static struct page *bufferpage;
>  static DEFINE_MUTEX(buffer_mutex);
>  
>  static int hwswitch_state;
> @@ -2097,12 +2096,11 @@ static int __init dell_init(void)
>  	 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
>  	 * is passed to SMI handler.
>  	 */
> -	bufferpage = alloc_page(GFP_KERNEL | GFP_DMA32);
> -	if (!bufferpage) {
> +	buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
> +	if (!buffer) {
>  		ret = -ENOMEM;
>  		goto fail_buffer;
>  	}
> -	buffer = page_address(bufferpage);
>  
>  	ret = dell_setup_rfkill();
>  
> @@ -2165,7 +2163,7 @@ static int __init dell_init(void)
>  fail_backlight:
>  	dell_cleanup_rfkill();
>  fail_rfkill:
> -	free_page((unsigned long)bufferpage);
> +	free_page((unsigned long)buffer);
>  fail_buffer:
>  	platform_device_del(platform_device);
>  fail_platform_device2:
> -- 
> 1.7.9.5
> 

-- 
Michal Hocko
SUSE Labs
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