linux-kernel - Re: [PATCH] wmi: use memcmp instead of strncmp to compare GUIDs

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Date:	Sun, 28 Nov 2010 23:31:57 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>
cc:	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	mjg@...hat.com, carlos@...angeworlds.co.uk, stable@...nel.org,
	ceolin@...vel.com
Subject: Re: [PATCH] wmi: use memcmp instead of strncmp to compare GUIDs

On Sun, 28 Nov 2010, Thadeu Lima de Souza Cascardo wrote:

> While looking for the duplicates in /sys/class/wmi/, I couldn't find
> them. The code that looks for duplicates uses strncmp in a binary GUID,
> which may contain zero bytes. The right function is memcmp, which is
> also used in another section of wmi code.
> 
> It was finding 49142400-C6A3-40FA-BADB-8A2652834100 as a duplicate of
> 39142400-C6A3-40FA-BADB-8A2652834100. Since the first byte is the fourth
> printed, they were found as equal by strncmp.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>
> ---
>  drivers/platform/x86/wmi.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 104b77c..aecd9a9 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -755,7 +755,7 @@ static bool guid_already_parsed(const char *guid_string)
>  	struct wmi_block *wblock;
>  
>  	list_for_each_entry(wblock, &wmi_block_list, list)
> -		if (strncmp(wblock->gblock.guid, guid_string, 16) == 0)
> +		if (memcmp(wblock->gblock.guid, guid_string, 16) == 0)
>  			return true;
>  
>  	return false;
> 

Looks right to me.

-- 
Jesper Juhl <jj@...osbits.net>            http://www.chaosbits.net/
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