linux-kernel - [PATCH 4.9 109/177] fbdev: controlfb: Add missing modes to fix out of bounds access

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Message-Id: <20171218152915.610199865@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:48:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 109/177] fbdev: controlfb: Add missing modes to fix out of bounds access

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/video/fbdev/controlfb.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/video/fbdev/controlfb.h
+++ b/drivers/video/fbdev/controlfb.h
@@ -141,5 +141,7 @@ static struct max_cmodes control_mac_mod
 	{{ 1, 2}},	/* 1152x870, 75Hz */
 	{{ 0, 1}},	/* 1280x960, 75Hz */
 	{{ 0, 1}},	/* 1280x1024, 75Hz */
+	{{ 1, 2}},	/* 1152x768, 60Hz */
+	{{ 0, 1}},	/* 1600x1024, 60Hz */
 };