From patchwork Fri Nov 20 23:14:19 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: 11922843 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 7A300C5519F for ; Fri, 20 Nov 2020 23:16:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 250CC22470 for ; Fri, 20 Nov 2020 23:16:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728761AbgKTXQI (ORCPT ); Fri, 20 Nov 2020 18:16:08 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:33444 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726719AbgKTXQG (ORCPT ); Fri, 20 Nov 2020 18:16:06 -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 1kgFdN-006Tng-AZ; Fri, 20 Nov 2020 16:16:05 -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 1kgFdM-00EG00-61; Fri, 20 Nov 2020 16:16:04 -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 17:14:19 -0600 Message-Id: <20201120231441.29911-2-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=1kgFdM-00EG00-61;;;mid=<20201120231441.29911-2-ebiederm@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX196u8wLHWhkRGE/DETQH7hBBNOxVYgWlQo= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v2 02/24] exec: Simplify unshare_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: linux-fsdevel@vger.kernel.org Now that exec no longer needs to return the unshared files to their previous value there is no reason to return displaced. Instead when unshare_fd creates a copy of the file table, call put_files_struct before returning from unshare_files. Acked-by: Christian Brauner v1: https://lkml.kernel.org/r/20200817220425.9389-2-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" --- fs/coredump.c | 5 +---- fs/exec.c | 5 +---- include/linux/fdtable.h | 2 +- kernel/fork.c | 12 ++++++------ 4 files changed, 9 insertions(+), 15 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 0cd9056d79cc..abf807235262 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -585,7 +585,6 @@ void do_coredump(const kernel_siginfo_t *siginfo) int ispipe; size_t *argv = NULL; int argc = 0; - struct files_struct *displaced; /* require nonrelative corefile path and be extra careful */ bool need_suid_safe = false; bool core_dumped = false; @@ -791,11 +790,9 @@ void do_coredump(const kernel_siginfo_t *siginfo) } /* get us an unshared descriptor table; almost always a no-op */ - retval = unshare_files(&displaced); + retval = unshare_files(); if (retval) goto close_fail; - if (displaced) - put_files_struct(displaced); if (!dump_interrupted()) { /* * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would diff --git a/fs/exec.c b/fs/exec.c index fa788988efe9..14fae2ec1c9d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1238,7 +1238,6 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) int begin_new_exec(struct linux_binprm * bprm) { struct task_struct *me = current; - struct files_struct *displaced; int retval; /* Once we are committed compute the creds */ @@ -1259,11 +1258,9 @@ int begin_new_exec(struct linux_binprm * bprm) goto out; /* Ensure the files table is not shared. */ - retval = unshare_files(&displaced); + retval = unshare_files(); if (retval) goto out; - if (displaced) - put_files_struct(displaced); /* * Must be called _before_ exec_mmap() as bprm->mm is diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index a32bf47c593e..f46a084b60b2 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -109,7 +109,7 @@ struct task_struct; struct files_struct *get_files_struct(struct task_struct *); void put_files_struct(struct files_struct *fs); void reset_files_struct(struct files_struct *); -int unshare_files(struct files_struct **); +int unshare_files(void); struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy; void do_close_on_exec(struct files_struct *); int iterate_fd(struct files_struct *, unsigned, diff --git a/kernel/fork.c b/kernel/fork.c index 32083db7a2a2..837b546528c8 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -3023,21 +3023,21 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) * the exec layer of the kernel. */ -int unshare_files(struct files_struct **displaced) +int unshare_files(void) { struct task_struct *task = current; - struct files_struct *copy = NULL; + struct files_struct *old, *copy = NULL; int error; error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©); - if (error || !copy) { - *displaced = NULL; + if (error || !copy) return error; - } - *displaced = task->files; + + old = task->files; task_lock(task); task->files = copy; task_unlock(task); + put_files_struct(old); return 0; }