Patch "fbdev: color map copying bounds checking" has been added to the 4.9-stable tree

Patch "fbdev: color map copying bounds checking" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    fbdev: color map copying bounds checking

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fbdev-color-map-copying-bounds-checking.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 2dc705a9930b4806250fbf5a76e55266e59389f2 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Tue, 24 Jan 2017 15:18:24 -0800
Subject: fbdev: color map copying bounds checking

From: Kees Cook <keescook@chromium.org>

commit 2dc705a9930b4806250fbf5a76e55266e59389f2 upstream.

Copying color maps to userspace doesn't check the value of to->start,
which will cause kernel heap buffer OOB read due to signedness wraps.

CVE-2016-8405

Link: http://lkml.kernel.org/r/20170105224249.GA50925@beast
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Peter Pi (@heisecode) of Trend Micro
Cc: Min Chong <mchong@google.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/video/fbdev/core/fbcmap.c |   26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

--- a/drivers/video/fbdev/core/fbcmap.c
+++ b/drivers/video/fbdev/core/fbcmap.c
@@ -163,17 +163,18 @@ void fb_dealloc_cmap(struct fb_cmap *cma
 
 int fb_copy_cmap(const struct fb_cmap *from, struct fb_cmap *to)
 {
-	int tooff = 0, fromoff = 0;
-	int size;
+	unsigned int tooff = 0, fromoff = 0;
+	size_t size;
 
 	if (to->start > from->start)
 		fromoff = to->start - from->start;
 	else
 		tooff = from->start - to->start;
-	size = to->len - tooff;
-	if (size > (int) (from->len - fromoff))
-		size = from->len - fromoff;
-	if (size <= 0)
+	if (fromoff >= from->len || tooff >= to->len)
+		return -EINVAL;
+
+	size = min_t(size_t, to->len - tooff, from->len - fromoff);
+	if (size == 0)
 		return -EINVAL;
 	size *= sizeof(u16);
 
@@ -187,17 +188,18 @@ int fb_copy_cmap(const struct fb_cmap *f
 
 int fb_cmap_to_user(const struct fb_cmap *from, struct fb_cmap_user *to)
 {
-	int tooff = 0, fromoff = 0;
-	int size;
+	unsigned int tooff = 0, fromoff = 0;
+	size_t size;
 
 	if (to->start > from->start)
 		fromoff = to->start - from->start;
 	else
 		tooff = from->start - to->start;
-	size = to->len - tooff;
-	if (size > (int) (from->len - fromoff))
-		size = from->len - fromoff;
-	if (size <= 0)
+	if (fromoff >= from->len || tooff >= to->len)
+		return -EINVAL;
+
+	size = min_t(size_t, to->len - tooff, from->len - fromoff);
+	if (size == 0)
 		return -EINVAL;
 	size *= sizeof(u16);
 


Patches currently in stable-queue which might be from keescook@chromium.org are

queue-4.9/fbdev-color-map-copying-bounds-checking.patch