patch "USB: core: harden cdc_parse_cdc_header" added to usb-linus

[<gregkh@linuxfoundation.org>]

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

    USB: core: harden cdc_parse_cdc_header

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 2e1c42391ff2556387b3cb6308b24f6f65619feb Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 21 Sep 2017 16:58:48 +0200
Subject: USB: core: harden cdc_parse_cdc_header

Andrey Konovalov reported a possible out-of-bounds problem for the
cdc_parse_cdc_header function.  He writes:
	It looks like cdc_parse_cdc_header() doesn't validate buflen
	before accessing buffer[1], buffer[2] and so on. The only check
	present is while (buflen > 0).

So fix this issue up by properly validating the buffer length matches
what the descriptor says it is.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/core/message.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 4c38ea41ae96..371a07d874a3 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -2069,6 +2069,10 @@ int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr,
 			elength = 1;
 			goto next_desc;
 		}
+		if ((buflen < elength) || (elength < 3)) {
+			dev_err(&intf->dev, "invalid descriptor buffer length\n");
+			break;
+		}
 		if (buffer[1] != USB_DT_CS_INTERFACE) {
 			dev_err(&intf->dev, "skipping garbage\n");
 			goto next_desc;
-- 
2.14.1