From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out02.mta.xmission.com ([166.70.13.232]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nrSZT-004C9R-2Q for linux-um@lists.infradead.org; Wed, 18 May 2022 22:55:12 +0000 From: "Eric W. Biederman" Date: Wed, 18 May 2022 17:53:51 -0500 Message-Id: <20220518225355.784371-12-ebiederm@xmission.com> In-Reply-To: <871qwq5ucx.fsf_-_@email.froward.int.ebiederm.org> References: <871qwq5ucx.fsf_-_@email.froward.int.ebiederm.org> MIME-Version: 1.0 Subject: [PATCH 12/16] ptrace: Stop protecting ptrace_set_signr with tasklist_lock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org 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 , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org, Robert OCallahan , Kyle Huey , Richard Henderson , Ivan Kokshaysky , Matt Turner , Jason Wessel , Daniel Thompson , Douglas Anderson , Douglas Miller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , "Eric W. Biederman" Now that ptrace_set_signr no longer sets task->exit_code the race documented in commit b72c186999e6 ("ptrace: fix race between ptrace_resume() and wait_task_stopped()") is no longer possible, as task->exit_code is only updated by wait during a ptrace_stop. As there is no possibilty of a race and ptrace_freeze_traced is all of the protection ptrace_set_signr needs to operate without contention move ptrace_set_signr outside of tasklist_lock and remove the documentation about the race that is no more. Signed-off-by: "Eric W. Biederman" --- kernel/ptrace.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index e0ecb1536dfc..d0527b6e2b29 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -595,17 +595,14 @@ static int ptrace_detach(struct task_struct *child, unsigned int data) /* Architecture-specific hardware disable .. */ ptrace_disable(child); + ptrace_set_signr(child, data); + write_lock_irq(&tasklist_lock); /* * We rely on ptrace_freeze_traced(). It can't be killed and * untraced by another thread, it can't be a zombie. */ WARN_ON(!child->ptrace || child->exit_state); - /* - * tasklist_lock avoids the race with wait_task_stopped(), see - * the comment in ptrace_resume(). - */ - ptrace_set_signr(child, data); __ptrace_detach(current, child); write_unlock_irq(&tasklist_lock); @@ -869,17 +866,9 @@ static int ptrace_resume(struct task_struct *child, long request, user_disable_single_step(child); } - /* - * Change ->exit_code and ->state under siglock to avoid the race - * with wait_task_stopped() in between; a non-zero ->exit_code will - * wrongly look like another report from tracee. - * - * Note that we need siglock even if ->exit_code == data and/or this - * status was not reported yet, the new status must not be cleared by - * wait_task_stopped() after resume. - */ - spin_lock_irq(&child->sighand->siglock); ptrace_set_signr(child, data); + + spin_lock_irq(&child->sighand->siglock); child->jobctl &= ~JOBCTL_TRACED; wake_up_state(child, __TASK_TRACED); spin_unlock_irq(&child->sighand->siglock); -- 2.35.3 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um