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[v2,(resend)] video: fbdev: fix OOB read in vga_8planes_imageblit()

Message ID 90b55ec3-d5b0-3307-9f7c-7ff5c5fd6ad3@i-love.sakura.ne.jp (mailing list archive)
State Superseded, archived
Headers show
Series [v2,(resend)] video: fbdev: fix OOB read in vga_8planes_imageblit() | expand

Commit Message

Tetsuo Handa Aug. 31, 2020, 10:37 a.m. UTC
syzbot is reporting OOB read at vga_8planes_imageblit() [1], for
"cdat[y] >> 4" can become a negative value due to "const char *cdat".

[1] https://syzkaller.appspot.com/bug?id=0d7a0da1557dcd1989e00cb3692b26d4173b4132

Reported-by: syzbot <syzbot+69fbd3e01470f169c8c4@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/video/fbdev/vga16fb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Tetsuo Handa Sept. 4, 2020, 2:53 p.m. UTC | #1
Hello, Greg.

Since nobody is interested in this bug, can you directly pick up
this obvious patch without waiting for maintainer's response?

On 2020/08/31 19:37, Tetsuo Handa wrote:
> syzbot is reporting OOB read at vga_8planes_imageblit() [1], for
> "cdat[y] >> 4" can become a negative value due to "const char *cdat".
> 
> [1] https://syzkaller.appspot.com/bug?id=0d7a0da1557dcd1989e00cb3692b26d4173b4132
> 
> Reported-by: syzbot <syzbot+69fbd3e01470f169c8c4@syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
>  drivers/video/fbdev/vga16fb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
> index a20eeb8308ff..578d3541e3d6 100644
> --- a/drivers/video/fbdev/vga16fb.c
> +++ b/drivers/video/fbdev/vga16fb.c
> @@ -1121,7 +1121,7 @@ static void vga_8planes_imageblit(struct fb_info *info, const struct fb_image *i
>          char oldop = setop(0);
>          char oldsr = setsr(0);
>          char oldmask = selectmask();
> -        const char *cdat = image->data;
> +	const unsigned char *cdat = image->data;
>  	u32 dx = image->dx;
>          char __iomem *where;
>          int y;
>
Greg KH Sept. 4, 2020, 3:24 p.m. UTC | #2
On Fri, Sep 04, 2020 at 11:53:16PM +0900, Tetsuo Handa wrote:
> Hello, Greg.
> 
> Since nobody is interested in this bug, can you directly pick up
> this obvious patch without waiting for maintainer's response?

I'll pick it up now.

thanks,

greg k-h
diff mbox series

Patch

diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
index a20eeb8308ff..578d3541e3d6 100644
--- a/drivers/video/fbdev/vga16fb.c
+++ b/drivers/video/fbdev/vga16fb.c
@@ -1121,7 +1121,7 @@  static void vga_8planes_imageblit(struct fb_info *info, const struct fb_image *i
         char oldop = setop(0);
         char oldsr = setsr(0);
         char oldmask = selectmask();
-        const char *cdat = image->data;
+	const unsigned char *cdat = image->data;
 	u32 dx = image->dx;
         char __iomem *where;
         int y;