linux-kernel - [PATCH 3.2 012/153] fbdev: Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in sbusfb_ioctl

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Message-ID: <lsq.1527677561.814339507@decadent.org.uk>
Date:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Peter Malone" <peter.malone@...il.com>,
        "Bartlomiej Zolnierkiewicz" <b.zolnierkie@...sung.com>,
        "Mathieu Malaterre" <malat@...ian.org>
Subject: [PATCH 3.2 012/153] fbdev: Fixing arbitrary kernel leak in case
 FBIOGETCMAP_SPARC in sbusfb_ioctl_helper().

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Peter Malone <peter.malone@...il.com>

commit 250c6c49e3b68756b14983c076183568636e2bde upstream.

Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in
sbusfb_ioctl_helper().

'index' is defined as an int in sbusfb_ioctl_helper().
We retrieve this from the user:
if (get_user(index, &c->index) ||
    __get_user(count, &c->count) ||
    __get_user(ured, &c->red) ||
    __get_user(ugreen, &c->green) ||
    __get_user(ublue, &c->blue))
       return -EFAULT;

and then we use 'index' in the following way:
red = cmap->red[index + i] >> 8;
green = cmap->green[index + i] >> 8;
blue = cmap->blue[index + i] >> 8;

This is a classic information leak vulnerability. 'index' should be
an unsigned int, given its usage above.

This patch is straight-forward; it changes 'index' to unsigned int
in two switch-cases: FBIOGETCMAP_SPARC && FBIOPUTCMAP_SPARC.

This patch fixes CVE-2018-6412.

Signed-off-by: Peter Malone <peter.malone@...il.com>
Acked-by: Mathieu Malaterre <malat@...ian.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/video/sbuslib.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/video/sbuslib.c
+++ b/drivers/video/sbuslib.c
@@ -122,7 +122,7 @@ int sbusfb_ioctl_helper(unsigned long cm
 		unsigned char __user *ured;
 		unsigned char __user *ugreen;
 		unsigned char __user *ublue;
-		int index, count, i;
+		unsigned int index, count, i;
 
 		if (get_user(index, &c->index) ||
 		    __get_user(count, &c->count) ||
@@ -161,7 +161,7 @@ int sbusfb_ioctl_helper(unsigned long cm
 		unsigned char __user *ugreen;
 		unsigned char __user *ublue;
 		struct fb_cmap *cmap = &info->cmap;
-		int index, count, i;
+		unsigned int index, count, i;
 		u8 red, green, blue;
 
 		if (get_user(index, &c->index) ||