2023-06-24 16:36:59

by Zhang Shurong

Subject: [PATCH] video: fbdev: fix potential OOB read in fast_imageblit()

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 <[email protected]>
---
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;
--
2.41.0

2023-06-24 20:18:32

by Helge Deller

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 <[email protected]>

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;