linux-kernel - Re: [PATCH] video: fbdev: fix potential OOB read in fast

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Message-ID: <bd436365-300c-a73c-7452-d874d7a279a6@gmx.de>
Date:   Sat, 24 Jun 2023 21:55:49 +0200
From:   Helge Deller <deller@....de>
To:     Zhang Shurong <zhang_shurong@...mail.com>, daniel@...ll.ch
Cc:     linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] video: fbdev: fix potential OOB read in fast_imageblit()

On 6/24/23 18:16, Zhang Shurong wrote:
> There is a potential OOB read at fast_imageblit, for
> "colortab[(*src >> 4)]" can become a negative value due to
> "const char *s = image->data, *src".
> This change makes sure the index for colortab always positive
> or zero.
>
> Similar commit:
> https://patchwork.kernel.org/patch/11746067
>
> Potential bug report:
> https://groups.google.com/g/syzkaller-bugs/c/9ubBXKeKXf4/m/k-QXy4UgAAAJ
>
> Signed-off-by: Zhang Shurong <zhang_shurong@...mail.com>

applied.

Thanks!
Helge

> ---
>   drivers/video/fbdev/core/sysimgblt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/sysimgblt.c b/drivers/video/fbdev/core/sysimgblt.c
> index 335e92b813fc..665ef7a0a249 100644
> --- a/drivers/video/fbdev/core/sysimgblt.c
> +++ b/drivers/video/fbdev/core/sysimgblt.c
> @@ -189,7 +189,7 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
>   	u32 fgx = fgcolor, bgx = bgcolor, bpp = p->var.bits_per_pixel;
>   	u32 ppw = 32/bpp, spitch = (image->width + 7)/8;
>   	u32 bit_mask, eorx, shift;
> -	const char *s = image->data, *src;
> +	const u8 *s = image->data, *src;
>   	u32 *dst;
>   	const u32 *tab;
>   	size_t tablen;