linux-kernel - RE: [PATCH] ST_CORE: Error triggered by convert "char" to "int"

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Date:	Thu, 10 Jan 2013 08:45:05 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	"Bi, Chao" <chao.bi@...el.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"pavan_savoy@...com" <pavan_savoy@...com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ST_CORE: Error triggered by convert "char" to "int"



> -----Original Message-----
> From: Bi, Chao
> Sent: Thursday, January 10, 2013 4:27 PM
> To: alan@...ux.intel.com; gregkh@...uxfoundation.org;
> akpm@...ux-foundation.org; pavan_savoy@...com
> Cc: Liu, Chuansheng; linux-kernel@...r.kernel.org
> Subject: [PATCH] ST_CORE: Error triggered by convert "char" to "int"
> 
> 
> When st driver decodes protocol index received from raw data,
> it does a value convert from "char" to "int". Because it's sign
> extension from bit8 to bit32, the "int" value maybe minus, in
> another word, the protocol index might be minus, but driver doesn't
> filter such case and may continue access memory pointed by this
> minus index.
> 
> This patch is to change the variable type of index from "int"
> to "unsigned char", so that it avoids do such kind of type
> conversion.
> 
Some infos:
when the type is minus, it will cause panic, because the below code
just consider type >= ST_MAX_CHANNELS case, no type < 0 case,
but it really happened.
			if ((type >= ST_MAX_CHANNELS) ||
					(st_gdata->list[type] == NULL)) {

Changing type from int to unsigned char can get benefit from the above
code.
If possible:
Acked-by: liu chuansheng <chuansheng.liu@...el.com>

Thanks.