fbdev: sbuslib: integer overflow in sbusfb_ioctl_helper()

Dan Carpenter · bzolnier · commit e5017716adb8 · 2018-10-08T12:57:36.000+02:00
The "index + count" addition can overflow.  Both come directly from the
user.  This bug leads to an information leak.

Signed-off-by: Dan Carpenter &lt;dan.carpenter@oracle.com&gt;
Cc: Peter Malone &lt;peter.malone@gmail.com&gt;
Cc: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Cc: Mathieu Malaterre &lt;malat@debian.org&gt;
Signed-off-by: Bartlomiej Zolnierkiewicz &lt;b.zolnierkie@samsung.com&gt;
diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
@@ -171,7 +171,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		    get_user(ublue, &c->blue))
 			return -EFAULT;
 
-		if (index + count > cmap->len)
+		if (index > cmap->len || count > cmap->len - index)
 			return -EINVAL;
 
 		for (i = 0; i < count; i++) {
