Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965118AbbD0SZ1 (ORCPT ); Mon, 27 Apr 2015 14:25:27 -0400 Received: from mout.gmx.net ([212.227.15.18]:64080 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964867AbbD0SZY (ORCPT ); Mon, 27 Apr 2015 14:25:24 -0400 Message-ID: <553E7F08.7070205@gmx.de> Date: Mon, 27 Apr 2015 20:25:12 +0200 From: Heinrich Schuchardt User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.6.0 MIME-Version: 1.0 To: Peter Chen CC: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] drivers/usb/chipidea/debuc.c: avoid out of bound read References: <1429250653-1626-1-git-send-email-xypron.glpk@gmx.de> <20150421013254.GA25710@shlinux2> <5536A435.1030808@gmx.de> <20150422012633.GA2680@shlinux2> In-Reply-To: <20150422012633.GA2680@shlinux2> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:Tqntx2CY7UCaahBP7RRhhNsPkZvVGkszlKmcGMBS+yUWLNRvUib J5ABHOya/UN7GLGdSzcPRv6ZbY4YdCFqqcSmBcmDL/xo4Pjz+r39CTYNFQ/ekO7B4g7VFRM kMoThOK0YdVnr320/8/jYXieAdT6u+69Uuhn8umkBnzSniLPuDiC0mHNSHTN230z47D6fFO /19nlKGyNimtAtSD4vLHQ== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2523 Lines: 96 On 22.04.2015 03:26, Peter Chen wrote: > On Tue, Apr 21, 2015 at 09:25:41PM +0200, Heinrich Schuchardt wrote: >> Hello Peter, >> >> thanks for reviewing. >> >> On 21.04.2015 03:32, Peter Chen wrote: >>> On Fri, Apr 17, 2015 at 08:04:13AM +0200, Heinrich Schuchardt wrote: >>>> A string written by the user may not be zero terminated. >>>> >>>> sscanf may read memory beyond the buffer if no zero byte >>>> is found. >>>> >>>> Signed-off-by: Heinrich Schuchardt >>>> --- >>>> drivers/usb/chipidea/debug.c | 6 +++++- >>>> 1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c >>>> index dfb05ed..ef08af3 100644 >>>> --- a/drivers/usb/chipidea/debug.c >>>> +++ b/drivers/usb/chipidea/debug.c >>>> @@ -88,9 +88,13 @@ static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf, >>>> char buf[32]; >>>> int ret; >>>> >>>> - if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count))) >>>> + count = min_t(size_t, sizeof(buf) - 1, count); >>>> + if (copy_from_user(buf, ubuf, count)) >>>> return -EFAULT; >>> >>> Any reasons to change above? >> >> Otherwise we would have two lines with the term >> min_t(size_t, sizeof(buf) - 1, count). > > Sorry, two lines of min_t(..)? Why I can't find it? Hello Peter, in my patch I write: count = min_t(size_t, sizeof(buf) - 1, count); if (copy_from_user(buf, ubuf, count)) return -EFAULT; /* sscanf requires a zero terminated string */ buf[count] = 0; Without the first part of the change I would have had to write: if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count))) return -EFAULT; /* sscanf requires a zero terminated string */ buf[min_t(size_t, sizeof(buf) - 1, count)] = 0; We should do the same calculation "min_t(size_t, sizeof(buf) - 1, count)" only once in the coding. Best regards Heinrich > > >> >> This would make the code harder to read. >> >>>> >>>> + /* sscanf requires a zero terminated string */ >>>> + buf[count] = 0; >>>> + >>> >>> I prefer using '\0' >> >> If you confirm the rest of the patch is ok, I will send an updated patch. >> >> Best regards >> >> Heinrich >> >>> >>>> if (sscanf(buf, "%u", &mode) != 1) >>>> return -EINVAL; >>>> >> > -- 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/