From patchwork Tue Apr 26 22:52:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 568724 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C54F6C433FE for ; Tue, 26 Apr 2022 22:53:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355936AbiDZW4N (ORCPT ); Tue, 26 Apr 2022 18:56:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355931AbiDZW4L (ORCPT ); Tue, 26 Apr 2022 18:56:11 -0400 Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA3374CD43; Tue, 26 Apr 2022 15:52:58 -0700 (PDT) Received: from in02.mta.xmission.com ([166.70.13.52]:33968) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njU3F-00FkCD-QZ; Tue, 26 Apr 2022 16:52:57 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:35772 helo=localhost.localdomain) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njU3E-006ASW-L9; Tue, 26 Apr 2022 16:52:57 -0600 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: rjw@rjwysocki.net, Oleg Nesterov , mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , inux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , "Eric W. Biederman" Date: Tue, 26 Apr 2022 17:52:07 -0500 Message-Id: <20220426225211.308418-5-ebiederm@xmission.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> MIME-Version: 1.0 X-XM-SPF: eid=1njU3E-006ASW-L9; ; ; mid=<20220426225211.308418-5-ebiederm@xmission.com>; ; ; hst=in02.mta.xmission.com; ; ; ip=68.227.174.4; ; ; frm=ebiederm@xmission.com; ; ; spf=softfail X-XM-AID: U2FsdGVkX19ApRYm2whcvnRl/iwUWilr3hK7QjBhNcc= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 5/9] signal: Protect parent child relationships by childs siglock 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-pm@vger.kernel.org The functions ptrace_stop and do_signal_stop have to drop siglock and grab tasklist_lock because the parent/child relation ship is guarded by siglock and not siglock. Simplify things by guarding the parent/child relationship with siglock. For the most part this just requires a little bit of code motion. In a couple of places more locking was needed. After this change tsk->parent, tsk->real_parent, tsk->ptrace tsk->ptracer_cred are all protected by tsk->siglock. The fields tsk->sibling and tsk->ptrace_entry are mostly protected by tsk->siglock. The field tsk->ptrace_entry is not protected by siglock when tsk->ptrace_entry is reused as the dead task list. The field tsk->sibling is not protected by siglock when children are reparented because their original parent dies. Signed-off-by: "Eric W. Biederman" --- kernel/exit.c | 4 ++++ kernel/fork.c | 12 ++++++------ kernel/ptrace.c | 13 +++++++++---- 3 files changed, 19 insertions(+), 10 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index f072959fcab7..b07af19eca13 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -643,11 +643,15 @@ static void forget_original_parent(struct task_struct *father, reaper = find_new_reaper(father, reaper); list_for_each_entry(p, &father->children, sibling) { + spin_lock(&p->sighand->siglock); for_each_thread(p, t) { RCU_INIT_POINTER(t->real_parent, reaper); BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father)); if (likely(!t->ptrace)) t->parent = t->real_parent; + } + spin_unlock(&p->sighand->siglock); + for_each_thread(p, t) { if (t->pdeath_signal) group_send_sig_info(t->pdeath_signal, SEND_SIG_NOINFO, t, diff --git a/kernel/fork.c b/kernel/fork.c index 9796897560ab..841021da69f3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2367,6 +2367,12 @@ static __latent_entropy struct task_struct *copy_process( */ write_lock_irq(&tasklist_lock); + klp_copy_process(p); + + sched_core_fork(p); + + spin_lock(¤t->sighand->siglock); + /* CLONE_PARENT re-uses the old parent */ if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { p->real_parent = current->real_parent; @@ -2381,12 +2387,6 @@ static __latent_entropy struct task_struct *copy_process( p->exit_signal = args->exit_signal; } - klp_copy_process(p); - - sched_core_fork(p); - - spin_lock(¤t->sighand->siglock); - /* * Copy seccomp details explicitly here, in case they were changed * before holding sighand lock. diff --git a/kernel/ptrace.c b/kernel/ptrace.c index ccc4b465775b..16d1a84a2cae 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -123,13 +123,12 @@ void __ptrace_unlink(struct task_struct *child) clear_task_syscall_work(child, SYSCALL_EMU); #endif + spin_lock(&child->sighand->siglock); child->parent = child->real_parent; list_del_init(&child->ptrace_entry); old_cred = child->ptracer_cred; child->ptracer_cred = NULL; put_cred(old_cred); - - spin_lock(&child->sighand->siglock); child->ptrace = 0; /* * Clear all pending traps and TRAPPING. TRAPPING should be @@ -447,15 +446,15 @@ static int ptrace_attach(struct task_struct *task, long request, if (task->ptrace) goto unlock_tasklist; + spin_lock(&task->sighand->siglock); task->ptrace = flags; ptrace_link(task, current); /* SEIZE doesn't trap tracee on attach */ if (!seize) - send_sig_info(SIGSTOP, SEND_SIG_PRIV, task); + send_signal_locked(SIGSTOP, SEND_SIG_PRIV, task, PIDTYPE_PID); - spin_lock(&task->sighand->siglock); /* * If the task is already STOPPED, set JOBCTL_TRAP_STOP and @@ -521,8 +520,10 @@ static int ptrace_traceme(void) * pretend ->real_parent untraces us right after return. */ if (!ret && !(current->real_parent->flags & PF_EXITING)) { + spin_lock(¤t->sighand->siglock); current->ptrace = PT_PTRACED; ptrace_link(current, current->real_parent); + spin_unlock(¤t->sighand->siglock); } } write_unlock_irq(&tasklist_lock); @@ -689,10 +690,14 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data) return ret; /* Avoid intermediate state when all opts are cleared */ + write_lock_irq(&tasklist_lock); + spin_lock(&child->sighand->siglock); flags = child->ptrace; flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT); flags |= (data << PT_OPT_FLAG_SHIFT); child->ptrace = flags; + spin_unlock(&child->sighand->siglock); + write_unlock_irq(&tasklist_lock); return 0; }