fbdev: sbuslib: integer overflow in sbusfb_ioctl_helper()

The "index + count" addition can overflow.  Both come directly from the
user.  This bug leads to an information leak.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Peter Malone <peter.malone@gmail.com>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
index 90c51330969c2f027b4e2e83f98457db7f0265cf..01a7110e61a76a19167fae82d71e1f9efdb312e3 100644 (file)
--- 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++) {