Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754599AbbDNLCK (ORCPT ); Tue, 14 Apr 2015 07:02:10 -0400 Received: from mail-la0-f48.google.com ([209.85.215.48]:32997 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479AbbDNLCA (ORCPT ); Tue, 14 Apr 2015 07:02:00 -0400 Message-ID: <552CF3A5.7040202@cogentembedded.com> Date: Tue, 14 Apr 2015 14:01:57 +0300 From: Sergei Shtylyov User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 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> <552BECD6.9090406@cogentembedded.com> In-Reply-To: <552BECD6.9090406@cogentembedded.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: 1875 Lines: 55 Hello. On 4/13/2015 7:20 PM, Sergei Shtylyov 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. s/operator/statement/, of course. :-) > [...] 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/