From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out03.mta.xmission.com ([166.70.13.233]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nrSZe-004CI4-RN for linux-um@lists.infradead.org; Wed, 18 May 2022 22:55:24 +0000 From: "Eric W. Biederman" Date: Wed, 18 May 2022 17:53:54 -0500 Message-Id: <20220518225355.784371-15-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 15/16] ptrace: Use siglock instead of tasklist_lock in ptrace_check_attach 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 siglock protects tsk->parent and tsk->ptrace there is no need to grab tasklist_lock in ptrace_check_attach. The siglock can handle all of the locking needs of ptrace_check_attach. Signed-off-by: "Eric W. Biederman" --- kernel/ptrace.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 77dfdb3d1ced..fa65841bbdbe 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -194,17 +194,14 @@ static bool ptrace_freeze_traced(struct task_struct *task) { bool ret = false; - /* Lockless, nobody but us can set this flag */ if (task->jobctl & JOBCTL_LISTENING) return ret; - spin_lock_irq(&task->sighand->siglock); if (task_is_traced(task) && !looks_like_a_spurious_pid(task) && !__fatal_signal_pending(task)) { task->jobctl |= JOBCTL_PTRACE_FROZEN; ret = true; } - spin_unlock_irq(&task->sighand->siglock); return ret; } @@ -240,32 +237,30 @@ static void ptrace_unfreeze_traced(struct task_struct *task) * state. * * CONTEXT: - * Grabs and releases tasklist_lock and @child->sighand->siglock. + * Grabs and releases @child->sighand->siglock. * * RETURNS: * 0 on success, -ESRCH if %child is not ready. */ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) { + unsigned long flags; int ret = -ESRCH; /* - * We take the read lock around doing both checks to close a + * We take the siglock around doing both checks to close a * possible race where someone else was tracing our child and * detached between these two checks. After this locked check, * we are sure that this is our traced child and that can only * be changed by us so it's not changing right after this. */ - read_lock(&tasklist_lock); - if (child->ptrace && child->parent == current) { - /* - * child->sighand can't be NULL, release_task() - * does ptrace_unlink() before __exit_signal(). - */ - if (ignore_state || ptrace_freeze_traced(child)) - ret = 0; + if (lock_task_sighand(child, &flags)) { + if (child->ptrace && child->parent == current) { + if (ignore_state || ptrace_freeze_traced(child)) + ret = 0; + } + unlock_task_sighand(child, &flags); } - read_unlock(&tasklist_lock); if (!ret && !ignore_state && WARN_ON_ONCE(!wait_task_inactive(child, __TASK_TRACED))) -- 2.35.3 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um