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 55B523F1656 for ; Mon, 24 Aug 2026 09:45:14 +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=1787564716; cv=none; b=qxnTivU1YVpYo62cdZN9TUYxWRPC/nfglxxJsUq5sykjxV6hcfR9zGT15PRKpaGyLwo5IOCVE+51Jyv8pqw6UwMdKJjjWaVaaChygLe+xXd55yJjwVBOKHjq1CERRRCJIaA8K0jZQSwL62JC+wYIBXg275l/5Utx7kliQt6GNyg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787564716; c=relaxed/simple; bh=65DgnvPIeAYH12/BdaFEO7AgdjuAwYK6kkmagDmrHlQ=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=bwLYkd8ZdHvbOBtyIXkIzKFuJzKZuks7nd6bGrMb+N4b5gEYFEUQLbIaSaDCvKvWDnIOb1UYVl2FQdUvEoHBM+mJekfpM/knUS3RtnXpmBsTFzFF162U+aSrZ8izx+KNzlDkZ8hU90lN5FmqY5Wi5ZP7ans6ftOQbJEuK5D4jVY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Lv/42o7k; 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="Lv/42o7k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4B1F1F000E9; Mon, 24 Aug 2026 09:45:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787564713; bh=HvmAlcztI+/lgaotbrM7NU/jt4YDJ3VNxdruji2A6AE=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=Lv/42o7k8cEJ/GwxQjJF1zb8+iNg/nrPUheBYct1bZTK/kv/ZrLRVA3+LPZXWA6Vj nj9q0zYvwufzkE2vTIYsdVRUTCum2gy9/aXRF2nL/Co6Li3UjzsmpAYuHRAZzzdmPh NmYvSIyUQU7U/qwIhoUFiP+TG8ZsXoqNgdytGea752clsV7lNc1GQHp9YigV8qW2F9 STDBCebGFcCYcHj/JgzkluZmqhpRmuBBR8Vho/RIaWFFEhRpUB+JfEPs0JrPP1jQFW F41zZd7tEkOHpA9PqTyZ1UGHbHkySmEKRExTYQf8aoPu4gq+L+mXSflB6RbXgtxNQ/ +umoHrzrXjEVA== From: Thomas Gleixner To: Hyunwoo Kim , oleg@redhat.com, frederic@kernel.org, brauner@kernel.org, peterz@infradead.org, anna-maria@linutronix.de, ebiederm@xmission.com Cc: linux-kernel@vger.kernel.org, imv4bel@gmail.com Subject: Re: [PATCH] signal: Use list_del_init_careful() in flush_sigqueue() In-Reply-To: <875x10hrkt.ffs@fw13> References: <875x10hrkt.ffs@fw13> Date: Mon, 24 Aug 2026 11:45:10 +0200 Message-ID: <8733w3j1i1.ffs@fw13> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, Aug 24 2026 at 10:04, Thomas Gleixner wrote: > On Sat, Aug 22 2026 at 14:37, Hyunwoo Kim wrote: >> diff --git a/kernel/signal.c b/kernel/signal.c >> index bbc0fd4cc4d7c1..ec9a0a0490d19f 100644 >> --- a/kernel/signal.c >> +++ b/kernel/signal.c >> @@ -482,7 +482,11 @@ void flush_sigqueue(struct sigpending *queue) >> sigemptyset(&queue->signal); >> while (!list_empty(&queue->list)) { >> q = list_entry(queue->list.next, struct sigqueue , list); >> - list_del_init(&q->list); >> + /* >> + * Pairs with the list_empty() in posixtimer_send_sigqueue(). > > No. That list_empty() would need to be changed to list_empty_careful() > to be correct on weakly ordered architectures. > > Aside of that I'm not convinced that this is the right way to handle > this as it cures the symptom and not the underlying problem. Let me > stare at this some more. Something like the untested below. Thanks, tglx --- --- a/fs/exec.c +++ b/fs/exec.c @@ -983,6 +983,18 @@ static int de_thread(struct task_struct } /* + * Ensure that POSIX timer SIGEV_THREAD_ID signals pending for + * the former leader are removed under sighand::siglock _before_ + * taking over the leader's TID. Otherwise the lockless cleanup + * in release_task() can race against a concurrent signal + * delivery to the new leader. The former leader has PF_EXITING + * set which prevents queueing of SIGEV_THREAD_ID signals up to + * the point where it's sighand gets cleared. + */ + scoped_guard(spinlock_irq, lock) + flush_sigqueue(&leader->pending); + + /* * The only record we have of the real-time age of a * process, regardless of execs it's done, is start_time. * All the past CPU time is accumulated in signal_struct --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1998,6 +1998,13 @@ void posixtimer_send_sigqueue(struct k_i return; /* + * If the signal is targeted at a specific thread, validate with sighand + * lock held that the thread is not exiting. + */ + if (unlikely(tmr->it_pid_type == PIDTYPE_PID && t->flags & PF_EXITING)) + goto unlock; + + /* * Update @tmr::sigqueue_seq for posix timer signals with sighand * locked to prevent a race against dequeue_signal(). */ @@ -2088,6 +2095,7 @@ void posixtimer_send_sigqueue(struct k_i result = TRACE_SIGNAL_DELIVERED; out: trace_signal_generate(sig, &q->info, t, tmr->it_pid_type != PIDTYPE_PID, result); +unlock: unlock_task_sighand(t, &flags); }