From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A98B5C282CE for ; Tue, 4 Jun 2019 12:46:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8279024C08 for ; Tue, 4 Jun 2019 12:46:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727845AbfFDMq1 (ORCPT ); Tue, 4 Jun 2019 08:46:27 -0400 Received: from www62.your-server.de ([213.133.104.62]:50958 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727709AbfFDMq1 (ORCPT ); Tue, 4 Jun 2019 08:46:27 -0400 Received: from [78.46.172.3] (helo=sslproxy06.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1hY8pa-00046h-T5; Tue, 04 Jun 2019 14:46:22 +0200 Received: from [178.197.249.21] (helo=linux.home) by sslproxy06.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1hY8pa-000BRN-Ma; Tue, 04 Jun 2019 14:46:22 +0200 Subject: Re: [PATCH] net: compat: fix msg_controllen overflow in scm_detach_fds_compat() To: Young Xiao <92siuyang@gmail.com> References: <1559651505-18137-1-git-send-email-92siuyang@gmail.com> Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, eric.dumazet@gmail.com From: Daniel Borkmann Message-ID: Date: Tue, 4 Jun 2019 14:46:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1559651505-18137-1-git-send-email-92siuyang@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.3/25470/Tue Jun 4 10:01:16 2019) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 06/04/2019 02:31 PM, Young Xiao wrote: > There is a missing check between kmsg->msg_controllen and cmlen, > which can possibly lead to overflow. > > This bug is similar to vulnerability that was fixed in commit 6900317f5eff > ("net, scm: fix PaX detected msg_controllen overflow in scm_detach_fds"). Back then I mentioned in commit 6900317f5eff: In case of MSG_CMSG_COMPAT (scm_detach_fds_compat()), I haven't seen an issue in my tests as alignment seems always on 4 byte boundary. Same should be in case of native 32 bit, where we end up with 4 byte boundaries as well. Do you have an actual reproducer or is it based on code inspection? > Signed-off-by: Young Xiao <92siuyang@gmail.com> > --- > net/compat.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/compat.c b/net/compat.c > index a031bd3..8e74dfb 100644 > --- a/net/compat.c > +++ b/net/compat.c > @@ -301,6 +301,8 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm) > err = put_user(cmlen, &cm->cmsg_len); > if (!err) { > cmlen = CMSG_COMPAT_SPACE(i * sizeof(int)); > + if (kmsg->msg_controllen < cmlen) > + cmlen = kmsg->msg_controllen; > kmsg->msg_control += cmlen; > kmsg->msg_controllen -= cmlen; > } >