[PATCH] fbdev: controlfb: Add missing modes to fix out of bounds access

[PATCH] fbdev: controlfb: Add missing modes to fix out of bounds access

[Geert Uytterhoeven]

Dan's static analysis says:

    drivers/video/fbdev/controlfb.c:560 control_setup()
    error: buffer overflow 'control_mac_modes' 20 <= 21

Indeed, control_mac_modes[] has only 20 elements, while VMODE_MAX is 22,
which may lead to an out of bounds read when parsing vmode commandline
options.

The bug was introduced in v2.4.5.6, when 2 new modes were added to
macmodes.h, but control_mac_modes[] wasn't updated:

https://kernel.opensuse.org/cgit/kernel/diff/include/video/macmodes.h?h=v2.5.2&id=29f279c764808560eaceb88fef36cbc35c529aad

Augment control_mac_modes[] with the two new video modes to fix this.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Compile-tested only.

The 1152x768 mode should be OK.
Given the 1600x1024 mode has a lower dotclock (112 MHz) than the
supported 1280x960 mode, it's probably OK, too.
---
 drivers/video/fbdev/controlfb.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/video/fbdev/controlfb.h b/drivers/video/fbdev/controlfb.h
index 6026c60fc1007e00..261522fabdac89ae 100644
--- a/drivers/video/fbdev/controlfb.h
+++ b/drivers/video/fbdev/controlfb.h
@@ -141,5 +141,7 @@ static struct max_cmodes control_mac_modes[] = {
 	{{ 1, 2}},	/* 1152x870, 75Hz */
 	{{ 0, 1}},	/* 1280x960, 75Hz */
 	{{ 0, 1}},	/* 1280x1024, 75Hz */
+	{{ 1, 2}},	/* 1152x768, 60Hz */
+	{{ 0, 1}},	/* 1600x1024, 60Hz */
 };
 
-- 
2.7.4

Re: [PATCH] fbdev: controlfb: Add missing modes to fix out of bounds access

[Bartlomiej Zolnierkiewicz]

On Tuesday, November 07, 2017 03:05:05 PM Geert Uytterhoeven wrote:
> Dan's static analysis says:
> 
>     drivers/video/fbdev/controlfb.c:560 control_setup()
>     error: buffer overflow 'control_mac_modes' 20 <= 21
> 
> Indeed, control_mac_modes[] has only 20 elements, while VMODE_MAX is 22,
> which may lead to an out of bounds read when parsing vmode commandline
> options.
> 
> The bug was introduced in v2.4.5.6, when 2 new modes were added to
> macmodes.h, but control_mac_modes[] wasn't updated:
> 
> https://kernel.opensuse.org/cgit/kernel/diff/include/video/macmodes.h?h=v2.5.2&id=29f279c764808560eaceb88fef36cbc35c529aad
> 
> Augment control_mac_modes[] with the two new video modes to fix this.
> 
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Patch queued for 4.15, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics