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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 2426FC433DF for ; Tue, 7 Jul 2020 12:38:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C9DA206F6 for ; Tue, 7 Jul 2020 12:38:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726757AbgGGMi6 (ORCPT ); Tue, 7 Jul 2020 08:38:58 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:39390 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725944AbgGGMi6 (ORCPT ); Tue, 7 Jul 2020 08:38:58 -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 1jsmsB-0008IT-CA; Tue, 07 Jul 2020 12:38:55 +0000 Date: Tue, 7 Jul 2020 14:38:54 +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 v6 5/7] fs: Expand __receive_fd() to accept existing fd Message-ID: <20200707123854.wi4s2kzwkhkgieyv@wittgenstein> References: <20200706201720.3482959-1-keescook@chromium.org> <20200706201720.3482959-6-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200706201720.3482959-6-keescook@chromium.org> Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, Jul 06, 2020 at 01:17:18PM -0700, Kees Cook wrote: > Expand __receive_fd() with support for replace_fd() for the coming seccomp > "addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior > and update existing wrappers to retain old behavior. > > Thanks to Colin Ian King for pointing out an > uninitialized variable exposure in an earlier version of this patch. > > Reviewed-by: Sargun Dhillon > Signed-off-by: Kees Cook > --- Thanks! (One tiny-nit below.) Acked-by: Christian Brauner > fs/file.c | 24 ++++++++++++++++++------ > include/linux/file.h | 10 +++++++--- > 2 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index 0efdcf413210..11313ff36802 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -937,6 +937,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > /** > * __receive_fd() - Install received file into file descriptor table > * > + * @fd: fd to install into (if negative, a new fd will be allocated) > * @file: struct file that was received from another process > * @ufd: __user pointer to write new fd number to > * @o_flags: the O_* flags to apply to the new fd entry > @@ -950,7 +951,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) > * > * Returns newly install fd or -ve on error. > */ > -int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > +int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags) > { > struct socket *sock; > int new_fd; > @@ -960,18 +961,30 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > if (error) > return error; > > - new_fd = get_unused_fd_flags(o_flags); > - if (new_fd < 0) > - return new_fd; > + if (fd < 0) { > + new_fd = get_unused_fd_flags(o_flags); > + if (new_fd < 0) > + return new_fd; > + } else > + new_fd = fd; This is nitpicky but coding style technically wants us to use braces around both branches if one of them requires them. ;) > > if (ufd) { > error = put_user(new_fd, ufd); > if (error) { > - put_unused_fd(new_fd); > + if (fd < 0) > + put_unused_fd(new_fd); > return error; > } > } > > + if (fd < 0) > + fd_install(new_fd, get_file(file)); > + else { > + error = replace_fd(new_fd, file, o_flags); > + if (error) > + return error; > + } > + > /* > * Bump the usage count and install the file. The resulting value of > * "error" is ignored here since we only need to take action when > @@ -982,7 +995,6 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags) > sock_update_netprioidx(&sock->sk->sk_cgrp_data); > sock_update_classid(&sock->sk->sk_cgrp_data); > } > - fd_install(new_fd, get_file(file)); > return new_fd; > } > > diff --git a/include/linux/file.h b/include/linux/file.h > index d9fee9f5c8da..225982792fa2 100644 > --- a/include/linux/file.h > +++ b/include/linux/file.h > @@ -92,18 +92,22 @@ extern void put_unused_fd(unsigned int fd); > > extern void fd_install(unsigned int fd, struct file *file); > > -extern int __receive_fd(struct file *file, int __user *ufd, > +extern int __receive_fd(int fd, struct file *file, int __user *ufd, > unsigned int o_flags); > static inline int receive_fd_user(struct file *file, int __user *ufd, > unsigned int o_flags) > { > if (ufd == NULL) > return -EFAULT; > - return __receive_fd(file, ufd, o_flags); > + return __receive_fd(-1, file, ufd, o_flags); > } > static inline int receive_fd(struct file *file, unsigned int o_flags) > { > - return __receive_fd(file, NULL, o_flags); > + return __receive_fd(-1, file, NULL, o_flags); > +} > +static inline int receive_fd_replace(int fd, struct file *file, unsigned int o_flags) > +{ > + return __receive_fd(fd, file, NULL, o_flags); > } > > extern void flush_delayed_fput(void); > -- > 2.25.1 >