linux-kernel - Re: [PATCH AUTOSEL 6.5 35/52] fbdev: core: syscopyarea: fix sloppy typing

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Date:   Mon, 30 Oct 2023 11:40:37 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Sasha Levin <sashal@...nel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
CC:     Helge Deller <deller@....de>, <daniel@...ll.ch>,
        <linux-fbdev@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH AUTOSEL 6.5 35/52] fbdev: core: syscopyarea: fix sloppy
 typing

On 10/30/23 1:53 AM, Sasha Levin wrote:

> From: Sergey Shtylyov <s.shtylyov@....ru>
> 
> [ Upstream commit e8e4a470b677511f9d1ad4f3cef32adc1d9a60ca ]
> 
> In sys_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/syscopyarea.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/core/syscopyarea.c b/drivers/video/fbdev/core/syscopyarea.c
> index c1eda31909682..7b8bd3a2bedc5 100644
> --- a/drivers/video/fbdev/core/syscopyarea.c
> +++ b/drivers/video/fbdev/core/syscopyarea.c
> @@ -316,7 +316,7 @@ void sys_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 *base = NULL;
>  	int bits = BITS_PER_LONG, bytes = bits >> 3;
>  	unsigned dst_idx = 0, src_idx = 0, rev_copy = 0;

   This one doesn't seem necessary in the stable kernels too...

MBR, Sergey