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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 66E62C433E0 for ; Mon, 22 Jun 2020 23:47:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CDA820738 for ; Mon, 22 Jun 2020 23:47:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731527AbgFVXr3 (ORCPT ); Mon, 22 Jun 2020 19:47:29 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54753 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730544AbgFVXqG (ORCPT ); Mon, 22 Jun 2020 19:46:06 -0400 Received: from ip5f5af08c.dynamic.kabel-deutschland.de ([95.90.240.140] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jnW8Z-0005DO-Ny; Mon, 22 Jun 2020 23:46:03 +0000 From: Christian Brauner To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Christian Brauner , Thomas Gleixner , Ingo Molnar , Al Viro , Geert Uytterhoeven , "Matthew Wilcox (Oracle)" , "Peter Zijlstra (Intel)" , linux-m68k@lists.linux-m68k.org, x86@kernel.org Subject: [PATCH 01/17] fork: fold legacy_clone_args_valid() into _do_fork() Date: Tue, 23 Jun 2020 01:43:10 +0200 Message-Id: <20200622234326.906346-2-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200622234326.906346-1-christian.brauner@ubuntu.com> References: <20200622234326.906346-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This separate helper only existed to guarantee the mutual exclusivity of CLONE_PIDFD and CLONE_PARENT_SETTID for legacy clone since CLONE_PIDFD abuses the parent_tid field to return the pidfd. But we can actually handle this uniformely thus removing the helper. For legacy clone we can detect that CLONE_PIDFD is specified in conjunction with CLONE_PARENT_SETTID because they will share the same memory which is invalid and for clone3() setting the separate pidfd and parent_tid fields to the same memory is bogus as well. So fold that helper directly into _do_fork() by detecting this case. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Al Viro Cc: Geert Uytterhoeven Cc: "Matthew Wilcox (Oracle)" Cc: "Peter Zijlstra (Intel)" Cc: linux-m68k@lists.linux-m68k.org Cc: x86@kernel.org Signed-off-by: Christian Brauner --- arch/m68k/kernel/process.c | 3 --- arch/x86/kernel/sys_ia32.c | 3 --- include/linux/sched/task.h | 1 - kernel/fork.c | 30 ++++++++++++++---------------- 4 files changed, 14 insertions(+), 23 deletions(-) diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c index 90ae376b7ab1..0608439ba452 100644 --- a/arch/m68k/kernel/process.c +++ b/arch/m68k/kernel/process.c @@ -125,9 +125,6 @@ asmlinkage int m68k_clone(struct pt_regs *regs) .tls = regs->d5, }; - if (!legacy_clone_args_valid(&args)) - return -EINVAL; - return _do_fork(&args); } diff --git a/arch/x86/kernel/sys_ia32.c b/arch/x86/kernel/sys_ia32.c index f8d65c99feb8..720cde885042 100644 --- a/arch/x86/kernel/sys_ia32.c +++ b/arch/x86/kernel/sys_ia32.c @@ -251,9 +251,6 @@ COMPAT_SYSCALL_DEFINE5(ia32_clone, unsigned long, clone_flags, .tls = tls_val, }; - if (!legacy_clone_args_valid(&args)) - return -EINVAL; - return _do_fork(&args); } #endif /* CONFIG_IA32_EMULATION */ diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 38359071236a..ddce0ea515d1 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -96,7 +96,6 @@ extern void exit_files(struct task_struct *); extern void exit_itimers(struct signal_struct *); extern long _do_fork(struct kernel_clone_args *kargs); -extern bool legacy_clone_args_valid(const struct kernel_clone_args *kargs); extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *); struct task_struct *fork_idle(int); struct mm_struct *copy_init_mm(void); diff --git a/kernel/fork.c b/kernel/fork.c index 142b23645d82..9875aeb2ba41 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2422,6 +2422,20 @@ long _do_fork(struct kernel_clone_args *args) int trace = 0; long nr; + /* + * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument + * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are + * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate + * field in struct clone_args and it still doesn't make sense to have + * them both point at the same memory location. Performing this check + * here has the advantage that we don't need to have a separate helper + * to check for legacy clone(). + */ + if ((args->flags & CLONE_PIDFD) && + (args->flags & CLONE_PARENT_SETTID) && + (args->pidfd == args->parent_tid)) + return -EINVAL; + /* * Determine whether and which event to report to ptracer. When * called from kernel_thread or CLONE_UNTRACED is explicitly @@ -2479,16 +2493,6 @@ long _do_fork(struct kernel_clone_args *args) return nr; } -bool legacy_clone_args_valid(const struct kernel_clone_args *kargs) -{ - /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */ - if ((kargs->flags & CLONE_PIDFD) && - (kargs->flags & CLONE_PARENT_SETTID)) - return false; - - return true; -} - #ifndef CONFIG_HAVE_COPY_THREAD_TLS /* For compatibility with architectures that call do_fork directly rather than * using the syscall entry points below. */ @@ -2508,9 +2512,6 @@ long do_fork(unsigned long clone_flags, .stack_size = stack_size, }; - if (!legacy_clone_args_valid(&args)) - return -EINVAL; - return _do_fork(&args); } #endif @@ -2593,9 +2594,6 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, .tls = tls, }; - if (!legacy_clone_args_valid(&args)) - return -EINVAL; - return _do_fork(&args); } #endif -- 2.27.0