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=-6.8 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 8678CC433DF for ; Mon, 6 Jul 2020 13:07:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F5A520724 for ; Mon, 6 Jul 2020 13:07:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729235AbgGFNHV (ORCPT ); Mon, 6 Jul 2020 09:07:21 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55535 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728940AbgGFNHT (ORCPT ); Mon, 6 Jul 2020 09:07:19 -0400 Received: from ip5f5af08c.dynamic.kabel-deutschland.de ([95.90.240.140] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jsQq3-0006Z1-3m; Mon, 06 Jul 2020 13:07:15 +0000 Date: Mon, 6 Jul 2020 15:07:13 +0200 From: Christian Brauner To: Kees Cook Cc: linux-kernel@vger.kernel.org, Sargun Dhillon , Christian Brauner , Tycho Andersen , David Laight , Christoph Hellwig , "David S. Miller" , Jakub Kicinski , Alexander Viro , Aleksa Sarai , Matt Denton , Jann Horn , Chris Palmer , Robert Sesek , Giuseppe Scrivano , Greg Kroah-Hartman , Andy Lutomirski , Will Drewry , Shuah Khan , netdev@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v5 4/7] pidfd: Replace open-coded partial fd_install_received() Message-ID: <20200706130713.n6r3vhn4hn2lodex@wittgenstein> References: <20200617220327.3731559-1-keescook@chromium.org> <20200617220327.3731559-5-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200617220327.3731559-5-keescook@chromium.org> Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Jun 17, 2020 at 03:03:24PM -0700, Kees Cook wrote: > The sock counting (sock_update_netprioidx() and sock_update_classid()) was > missing from pidfd's implementation of received fd installation. Replace > the open-coded version with a call to the new fd_install_received() > helper. > > Fixes: 8649c322f75c ("pid: Implement pidfd_getfd syscall") > Signed-off-by: Kees Cook > --- > kernel/pid.c | 11 +---------- > 1 file changed, 1 insertion(+), 10 deletions(-) > > diff --git a/kernel/pid.c b/kernel/pid.c > index f1496b757162..24924ec5df0e 100644 > --- a/kernel/pid.c > +++ b/kernel/pid.c > @@ -635,18 +635,9 @@ static int pidfd_getfd(struct pid *pid, int fd) > if (IS_ERR(file)) > return PTR_ERR(file); > > - ret = security_file_receive(file); > - if (ret) { > - fput(file); > - return ret; > - } > - > - ret = get_unused_fd_flags(O_CLOEXEC); > + ret = fd_install_received(file, O_CLOEXEC); > if (ret < 0) > fput(file); > - else > - fd_install(ret, file); So someone just sent a fix for pidfd_getfd() that was based on the changes done here. I've been on vacation so didn't have a change to review this series and I see it's already in linux-next. This introduces a memory leak and actually proves a point I tried to stress when adding this helper: fd_install_received() in contrast to fd_install() does _not_ consume a reference because it takes one before it calls into fd_install(). That means, you need an unconditional fput() here both in the failure and error path. I strongly suggest though that we simply align the behavior between fd_install() and fd_install_received() and have the latter simply consume a reference when it succeeds! Imho, this bug proves that I was right to insist on this before. ;) Thanks! Christian