Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751237AbdFANur (ORCPT ); Thu, 1 Jun 2017 09:50:47 -0400 Received: from mail-vk0-f50.google.com ([209.85.213.50]:34041 "EHLO mail-vk0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751149AbdFANup (ORCPT ); Thu, 1 Jun 2017 09:50:45 -0400 MIME-Version: 1.0 In-Reply-To: <20170601134737.7dp2pbnek26b6kqf@yury-thinkpad> References: <20170601123829.51794-1-glider@google.com> <20170601134737.7dp2pbnek26b6kqf@yury-thinkpad> From: Alexander Potapenko Date: Thu, 1 Jun 2017 15:50:33 +0200 Message-ID: Subject: Re: [PATCH v3] net: don't call strlen on non-terminated string in dev_set_alias() To: Yury Norov Cc: Dmitriy Vyukov , Kostya Serebryany , Eric Dumazet , David Miller , stephen@networkplumber.org, LKML , Networking 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-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v51Dp09g024553 Content-Length: 1693 Lines: 54 On Thu, Jun 1, 2017 at 3:47 PM, Yury Norov wrote: > On Thu, Jun 01, 2017 at 02:38:29PM +0200, Alexander Potapenko wrote: >> KMSAN reported a use of uninitialized memory in dev_set_alias(), >> which was caused by calling strlcpy() (which in turn called strlen()) >> on the user-supplied non-terminated string. >> >> Signed-off-by: Alexander Potapenko >> --- >> v3: removed the multi-line comment >> v2: fixed an off-by-one error spotted by Dmitry Vyukov > > [...] > >> --- >> net/core/dev.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/net/core/dev.c b/net/core/dev.c >> index fca407b4a6ea..3e3b29133cc9 100644 >> --- a/net/core/dev.c >> +++ b/net/core/dev.c >> @@ -1254,7 +1254,9 @@ int dev_set_alias(struct net_device *dev, const char *alias, size_t len) >> return -ENOMEM; >> dev->ifalias = new_ifalias; >> >> - strlcpy(dev->ifalias, alias, len+1); >> + /* alias comes from the userspace and may not be zero-terminated. */ > > So if the comment is correct, you'd use copy_from_user() instead. Well, the contents of |alias| have been previously copied from the userspace, but this is a pointer to a kernel buffer, as the function prototype tells. Do you think a confusion is possible here? >> + memcpy(dev->ifalias, alias, len); >> + dev->ifalias[len] = 0; >> return len; >> } >> >> -- >> 2.13.0.219.gdb65acc882-goog -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg