Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933626AbbEKTAM (ORCPT ); Mon, 11 May 2015 15:00:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36354 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752867AbbEKRzt (ORCPT ); Mon, 11 May 2015 13:55:49 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Phil Turnbull , Quentin Casasnovas , Sergei Shtylyov , Oliver Neukum , Adam Lee Subject: [PATCH 4.0 36/72] cdc-acm: prevent infinite loop when parsing CDC headers. Date: Mon, 11 May 2015 10:54:42 -0700 Message-Id: <20150511175438.176819085@linuxfoundation.org> X-Mailer: git-send-email 2.4.0 In-Reply-To: <20150511175437.112151861@linuxfoundation.org> References: <20150511175437.112151861@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2061 Lines: 62 4.0-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 --- drivers/usb/class/cdc-acm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1133,11 +1133,16 @@ static int acm_probe(struct usb_interfac } 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/