linux-kernel - Re: [PATCH AUTOSEL 6.5 34/52] fbdev: core: cfbcopyarea: fix sloppy typing

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Message-ID: <ZUWnasfAphVCFPhR@sashalap>
Date:   Fri, 3 Nov 2023 22:07:38 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Helge Deller <deller@....de>, daniel@...ll.ch,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH AUTOSEL 6.5 34/52] fbdev: core: cfbcopyarea: fix sloppy
 typing

On Mon, Oct 30, 2023 at 11:39:14AM +0300, Sergey Shtylyov wrote:
>Hello!
>
>On 10/30/23 1:53 AM, Sasha Levin wrote:
>
>> From: Sergey Shtylyov <s.shtylyov@....ru>
>>
>> [ Upstream commit 7f33df94cf0156f64eee9509bd9b4a178990f613 ]
>>
>> In cfb_copyarea(), the local variable bits_per_line is needlessly typed as
>> *unsigned long* -- which is a 32-bit type on the 32-bit arches and a 64-bit
>> type on the 64-bit arches; that variable's value is derived from the __u32
>> typed fb_fix_screeninfo::line_length field (multiplied by 8u) and a 32-bit
>> *unsigned int* type should still be enough to store the # of bits per line.
>>
>> Found by Linux Verification Center (linuxtesting.org) with the Svace static
>> analysis tool.
>>
>> Signed-off-by: Sergey Shtylyov <s.shtylyov@....ru>
>> Signed-off-by: Helge Deller <deller@....de>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  drivers/video/fbdev/core/cfbcopyarea.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/fbdev/core/cfbcopyarea.c b/drivers/video/fbdev/core/cfbcopyarea.c
>> index 6d4bfeecee350..5b80bf3dae504 100644
>> --- a/drivers/video/fbdev/core/cfbcopyarea.c
>> +++ b/drivers/video/fbdev/core/cfbcopyarea.c
>> @@ -382,7 +382,7 @@ void cfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
>>  {
>>  	u32 dx = area->dx, dy = area->dy, sx = area->sx, sy = area->sy;
>>  	u32 height = area->height, width = area->width;
>> -	unsigned long const bits_per_line = p->fix.line_length*8u;
>> +	unsigned int const bits_per_line = p->fix.line_length * 8u;
>>  	unsigned long __iomem *base = NULL;
>>  	int bits = BITS_PER_LONG, bytes = bits >> 3;
>>  	unsigned dst_idx = 0, src_idx = 0, rev_copy = 0;
>
>   I highly doubt this is necessary to pull that into stable. This was
>intended to be a cleanup originally.

I'll drop this and the other one you've pointed out, thanks!

-- 
Thanks,
Sasha