Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932296AbbDMPW3 (ORCPT ); Mon, 13 Apr 2015 11:22:29 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:46410 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932201AbbDMPW1 (ORCPT ); Mon, 13 Apr 2015 11:22:27 -0400 From: Quentin Casasnovas To: lkml Cc: linux-usb , Quentin Casasnovas , Phil Turnbull , Oliver Neukum , Adam Lee Subject: [PATCH] cdc-acm: prevent infinite loop when parsing CDC headers. Date: Mon, 13 Apr 2015 17:24:04 +0200 Message-Id: <1428938644-19942-1-git-send-email-quentin.casasnovas@oracle.com> X-Mailer: git-send-email 2.0.5 X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1738 Lines: 50 Phil and I found out a problem with commit: 7e860a6e ("cdc-acm: add sanity checks") It added some sanity checks to ignore potential garbage in CDC headers but also introduced a potential infinite loop. This can happen at the first loop iteration (elength = 0 in that case) if the description isn't a DT_CS_INTERFACE or later if 'buffer[0]' is zero. It should also be noted that the wrong length was being added to 'buffer' in case 'buffer[1]' was not a DT_CS_INTERFACE descriptor, since elength was assigned after that check in the loop. A specially crafted USB device could be used to trigger this infinite loop. Fixes: 7e860a6e ("cdc-acm: add sanity checks") Signed-off-by: Phil Turnbull Signed-off-by: Quentin Casasnovas CC: Oliver Neukum CC: Adam Lee --- drivers/usb/class/cdc-acm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 6836177..1ac4587 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1133,11 +1133,12 @@ static int acm_probe(struct usb_interface *intf, } while (buflen > 0) { + if ((elength = buffer[0]) == 0) + break; if (buffer[1] != USB_DT_CS_INTERFACE) { dev_err(&intf->dev, "skipping garbage\n"); goto next_desc; } - elength = buffer[0]; switch (buffer[2]) { case USB_CDC_UNION_TYPE: /* we've found it */ -- 2.0.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/