Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932571AbbDMQUo (ORCPT ); Mon, 13 Apr 2015 12:20:44 -0400 Received: from mail-lb0-f169.google.com ([209.85.217.169]:34096 "EHLO mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754005AbbDMQUm (ORCPT ); Mon, 13 Apr 2015 12:20:42 -0400 Message-ID: <552BECD6.9090406@cogentembedded.com> Date: Mon, 13 Apr 2015 19:20:38 +0300 From: Sergei Shtylyov Organization: Cogent Embedded User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Quentin Casasnovas , lkml CC: linux-usb , Phil Turnbull , Oliver Neukum , Adam Lee Subject: Re: [PATCH] cdc-acm: prevent infinite loop when parsing CDC headers. References: <1428938644-19942-1-git-send-email-quentin.casasnovas@oracle.com> In-Reply-To: <1428938644-19942-1-git-send-email-quentin.casasnovas@oracle.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1790 Lines: 53 Hello. On 04/13/2015 06:24 PM, Quentin Casasnovas wrote: > 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") 12-digit SHA1 hash is required here. > 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) Please run your patches thru scripts/checkpatch.pl. Assignments in the *if* operator are not allowed. [...] WBR, Sergei -- 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/