From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1562A46D2DA for ; Fri, 11 Sep 2026 09:09:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789117785; cv=none; b=oGWfyVJ6LfRReBZtqgAcUuAZukKyU4EbefgiVmL+aJ5q6/WYrv4yrwtLj371s3+wSQ9c8qdGZ7OcuwMxMcRmhcxqRsOgAzB1wenaEoUQOtzwmLiXQ/BfnSJxZDLlSOuYYR5pXIIMwF/m5tBENXgeo80atelozVAvsFBlaHSPw8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789117785; c=relaxed/simple; bh=pilVMOERfyY22QKpbhtG99+BWInIBpqe64C/M9IYHp4=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=ZuE7GqrV0e9cRAs3H0l3Pmucg8GOclR4HT/vkCifPWQuWomBcd/4gU9zgCeEGZOFrGvym9UZvzvxAWuCtY/F1B8gY2HBoB3WIMxNyAtIOnownwAbl7vHehtrdupixUrI2ZxtLcqgq6ceZN0gUxN4mQJ2V4mreS23EPqBi7K1/YU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F7i0MZmn; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F7i0MZmn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 677811F000FF; Fri, 11 Sep 2026 09:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789117783; bh=0KZHuvDVKADmlpo57k3z+qU0GhL8yEajgLzPcs18XCA=; h=Date:From:To:Cc:Subject:References; b=F7i0MZmnqihZQ/Mml9RDYnIrt8EfEQYVxRQllVeOUZsxRSah9DO7CbZ8vkYjLd8Lq ps+e5JqTyIDWdnX7hSDFYnl/ybz2hgrTvTzBFsQhq+cUhNI6anafy57ncznyVtgoC4 d4+uie7a0C67Pc/Zzw9tC6RuwB8K46bWvD6kve5yhtZp+9qo+nkI+MAxJD8h0eNhg8 GkimWJyU8vqThS40Q/uuuzAEelsYC5DpablyMDgAgoOkgr/tzJNoaagbZQnR4IkAtN w57EixCZp57yMe13iR7cAgo36ULOpI5Og0c8MtbM39/Ckwm+9ScLGJVi30BDHa/dwF 1gY6ZscqlHwYg== Date: Fri, 11 Sep 2026 11:09:40 +0200 Message-ID: <20260911090541.892445443@kernel.org> User-Agent: quilt/0.69 From: Thomas Gleixner To: LKML Cc: Hyunwoo Kim , Oleg Nesterov , Frederic Weisbecker , Christian Brauner , Peter Zijlstra , John Stultz , Ingo Molnar , Alexander Viro , "Eric W. Biederman" , Alan Stern Subject: [patch V3 7/8] posix-cpu-timers: Prevent enqueueing when PF_EXITING is set References: <20260911090341.949101445@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Thomas Gleixner To prepare for cleaning up POSIX CPU timers in do_exit(), prevent enqueueing POSIX CPU timers on a task which has PF_EXITING set. Queueing a timer on such a task is pointless because the task won't expire the timer anymore. The same applies to process wide timers when tsk::signal::flags has SIGNAL_GROUP_EXIT set. Pretending that the timer is armed allows to keep the POSIX timer mechanism "working" so that the timer stays accessible up to the point where a task is unhashed. Signed-off-by: Thomas Gleixner Reviewed-by: Oleg Nesterov --- kernel/time/posix-cpu-timers.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -628,6 +628,7 @@ static int posix_cpu_timer_del(struct k_ } if (!ret) { + WARN_ON_ONCE(cpu_timer_queued(&timer->it.cpu)); put_pid(timer->it.cpu.pid); timer->it_status = POSIX_TIMER_DISARMED; } @@ -675,6 +676,27 @@ void posix_cpu_timers_exit_group(struct } /* + * This function validates that POSIX CPU timers can be safely enqueued on the + * target task. + * + * Enqueue is allowed when PF_EXITING is not set. If set then it is only allowed + * for process shared timers (type = PIDTYPE_TGID) as long as tsk::signal::flags + * does not have SIGNAL_GROUP_EXIT set. PIDTYPE_PID targets are not allowed at + * all when the task has PF_EXITING set. + * + * This guarantees that after the POSIX timer cleanup in posixtimer_exit() no + * POSIX CPU timers are queued on the task or in case of a group exit on the + * process. + */ +static inline bool task_can_enqueue_timer(struct task_struct *tsk, enum pid_type type) +{ + if (likely(!(tsk->flags & PF_EXITING))) + return true; + + return type == PIDTYPE_TGID && !(tsk->signal->flags & SIGNAL_GROUP_EXIT); +} + +/* * Insert the timer on the appropriate list before any timers that * expire later. This must be called with the sighand lock held. */ @@ -684,7 +706,13 @@ static void arm_timer(struct k_itimer *t struct cpu_timer *ctmr = &timer->it.cpu; u64 newexp = cpu_timer_getexpires(ctmr); + lockdep_assert_held(&p->sighand->siglock); + timer->it_status = POSIX_TIMER_ARMED; + + if (unlikely(!task_can_enqueue_timer(p, clock_pid_type(timer->it_clock)))) + return; + if (!cpu_timer_enqueue(&base->tqhead, ctmr)) return;