From patchwork Fri Nov 20 23:14:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11922811 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 B0B82C6379D for ; Fri, 20 Nov 2020 23:17:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 641A62240B for ; Fri, 20 Nov 2020 23:17:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729264AbgKTXQ2 (ORCPT ); Fri, 20 Nov 2020 18:16:28 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:33648 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729241AbgKTXQ1 (ORCPT ); Fri, 20 Nov 2020 18:16:27 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1kgFdi-006TqE-8D; Fri, 20 Nov 2020 16:16:26 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.int.ebiederm.org) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1kgFdg-00EG00-RF; Fri, 20 Nov 2020 16:16:25 -0700 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, criu@openvz.org, bpf@vger.kernel.org, Linus Torvalds , Alexander Viro , Christian Brauner , Oleg Nesterov , Cyrill Gorcunov , Jann Horn , Kees Cook , =?utf-8?q?Da?= =?utf-8?q?niel_P_=2E_Berrang=C3=A9?= , Jeff Layton , Miklos Szeredi , Matthew Wilcox , "J. Bruce Fields" , Trond Myklebust , Chris Wright , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , "Eric W. Biederman" Date: Fri, 20 Nov 2020 17:14:25 -0600 Message-Id: <20201120231441.29911-8-ebiederm@xmission.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <87r1on1v62.fsf@x220.int.ebiederm.org> References: <87r1on1v62.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 X-XM-SPF: eid=1kgFdg-00EG00-RF;;;mid=<20201120231441.29911-8-ebiederm@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18edY7AsNzDid9bgwd2GH9BMu//oTEEyxM= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v2 08/24] file: Factor files_lookup_fd_locked out of fcheck_files X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org To make it easy to tell where files->file_lock protection is being used when looking up a file create files_lookup_fd_locked. Only allow this function to be called with the file_lock held. Update the callers of fcheck and fcheck_files that are called with the files->file_lock held to call files_lookup_fd_locked instead. Hopefully this makes it easier to quickly understand what is going on. The need for better names became apparent in the last round of discussion of this set of changes[1]. [1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqyQ@mail.gmail.com Signed-off-by: "Eric W. Biederman" --- fs/file.c | 2 +- fs/locks.c | 14 ++++++++------ fs/proc/fd.c | 2 +- include/linux/fdtable.h | 7 +++++++ 4 files changed, 17 insertions(+), 8 deletions(-) diff --git a/fs/file.c b/fs/file.c index b5591efb87f5..9d0e91168be1 100644 --- a/fs/file.c +++ b/fs/file.c @@ -1098,7 +1098,7 @@ static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) spin_lock(&files->file_lock); err = expand_files(files, newfd); - file = fcheck(oldfd); + file = files_lookup_fd_locked(files, oldfd); if (unlikely(!file)) goto Ebadf; if (unlikely(err < 0)) { diff --git a/fs/locks.c b/fs/locks.c index 1f84a03601fe..148197c1b547 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -2539,14 +2539,15 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, */ if (!error && file_lock->fl_type != F_UNLCK && !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; /* * We need that spin_lock here - it prevents reordering between * update of i_flctx->flc_posix and check for it done in * close(). rcu_read_lock() wouldn't do. */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); if (f != filp) { file_lock->fl_type = F_UNLCK; error = do_lock_file_wait(filp, cmd, file_lock); @@ -2670,14 +2671,15 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, */ if (!error && file_lock->fl_type != F_UNLCK && !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; /* * We need that spin_lock here - it prevents reordering between * update of i_flctx->flc_posix and check for it done in * close(). rcu_read_lock() wouldn't do. */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); if (f != filp) { file_lock->fl_type = F_UNLCK; error = do_lock_file_wait(filp, cmd, file_lock); diff --git a/fs/proc/fd.c b/fs/proc/fd.c index d58960f6ee52..2cca9bca3b3a 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -35,7 +35,7 @@ static int seq_show(struct seq_file *m, void *v) unsigned int fd = proc_fd(m->private); spin_lock(&files->file_lock); - file = fcheck_files(files, fd); + file = files_lookup_fd_locked(files, fd); if (file) { struct fdtable *fdt = files_fdtable(files); diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 639933f37da9..fda4b81dd735 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -91,6 +91,13 @@ static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsig return NULL; } +static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd) +{ + RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock), + "suspicious rcu_dereference_check() usage"); + return files_lookup_fd_raw(files, fd); +} + static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd) { RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&