linux-kernel - [PATCH AUTOSEL for 4.4 052/101] fbdev: controlfb: Add missing modes to fix out of bounds access

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Message-ID: <20171207155005.5852-52-alexander.levin@verizon.com>
Date:   Thu, 7 Dec 2017 15:50:24 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.4 052/101] fbdev: controlfb: Add missing modes
 to fix out of bounds access

From: Geert Uytterhoeven <geert@...ux-m68k.org>

[ Upstream commit ac831a379d34109451b3c41a44a20ee10ecb615f ]

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@...cle.com>
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 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 6026c60fc100..261522fabdac 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 */
 };
 
-- 
2.11.0