fbdev: sbuslib: integer overflow in sbusfb_ioctl_helper()

[ Upstream commit e5017716adb8aa5c01c52386c1b7470101ffe9c5 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
index b425718925c0158a85c9f8d7edc3befa9702d4a6..52e161dbd204781ae06a5f31c5bad95b46224b6e 100644 (file)
--- a/drivers/video/fbdev/sbuslib.c
+++ b/drivers/video/fbdev/sbuslib.c
@@ -170,7 +170,7 @@ 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++) {