Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757019AbbEVJlH (ORCPT ); Fri, 22 May 2015 05:41:07 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:34889 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756928AbbEVI7G (ORCPT ); Fri, 22 May 2015 04:59:06 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Phil Turnbull , Quentin Casasnovas , Sergei Shtylyov , Oliver Neukum , Adam Lee , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 3.16.y-ckt 026/129] cdc-acm: prevent infinite loop when parsing CDC headers. Date: Fri, 22 May 2015 09:56:51 +0100 Message-Id: <1432285114-9254-27-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> References: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2245 Lines: 62 3.16.7-ckt12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Quentin Casasnovas commit 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e upstream. Phil and I found out a problem with commit: 7e860a6e7aa6 ("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: 7e860a6e7aa6 ("cdc-acm: add sanity checks") Signed-off-by: Phil Turnbull Signed-off-by: Quentin Casasnovas CC: Sergei Shtylyov CC: Oliver Neukum CC: Adam Lee Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luis Henriques --- drivers/usb/class/cdc-acm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index bc2cacd3cb68..a8946e88978e 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1128,11 +1128,16 @@ static int acm_probe(struct usb_interface *intf, } while (buflen > 0) { + elength = buffer[0]; + if (!elength) { + dev_err(&intf->dev, "skipping garbage byte\n"); + elength = 1; + goto next_desc; + } 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 */ -- 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/