From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 ACE927482; Mon, 23 Jun 2025 21:16:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713370; cv=none; b=sqwPddlzA3w0NPVU3AfQXAuchdabI2dX+axMY7pM+JUXVBRS5MoI1LezvhXLxaDuLCUZxsxY1hGS49wcP4O8+bs1soukcYCRIsIkSZUEJ6HsGKfwv4hmarqkPSvCqzKu/2QdqWq69T7tysNYXDoOG8ZUcjXctmdHRj1rYRD0HcY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713370; c=relaxed/simple; bh=UaIUNznorEkse28JALflmvsFp2JJFkHHrfgWpVpeIds=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bl1hVAAJ+WRBMAf9OS2S4HFIrxNesfinUDvYBuVLJrUWKRu/MV4qyDl+cUfWcw4mj44z7KSBxhrtQlWliZtNk/LuKVK5DHYtQ7CY8ytEAkPHlhIRQG859nLRhMDQwwZIUnOsRl4trUACF0dAs98jlfN6zRvJaHur74SRbhnkTS4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PRGxz5eK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="PRGxz5eK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 425A2C4CEEA; Mon, 23 Jun 2025 21:16:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750713370; bh=UaIUNznorEkse28JALflmvsFp2JJFkHHrfgWpVpeIds=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PRGxz5eK2MxMkU/rtrVb7g4VF6LLTPJRZoSqty3aNFQQKaP7YNhMfdqL5/lexd7Ce QMBy6f13EA66semjfqrD8tRPVFH2t7iq4g3i1ZasE7onpxzhwgnEsu7AaBMasINcGi HVLYKTGcJFooC4jOW3Dld0ejaesHMZkNFmnexcNc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Beno=C3=AEt=20Sevens?= , Oleg Nesterov , Linus Torvalds Subject: [PATCH 5.10 140/355] posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() Date: Mon, 23 Jun 2025 15:05:41 +0200 Message-ID: <20250623130630.928893871@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130626.716971725@linuxfoundation.org> References: <20250623130626.716971725@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov commit f90fff1e152dedf52b932240ebbd670d83330eca upstream. If an exiting non-autoreaping task has already passed exit_notify() and calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent or debugger right after unlock_task_sighand(). If a concurrent posix_cpu_timer_del() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or lock_task_sighand() will fail. Add the tsk->exit_state check into run_posix_cpu_timers() to fix this. This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because exit_task_work() is called before exit_notify(). But the check still makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail anyway in this case. Cc: stable@vger.kernel.org Reported-by: Benoît Sevens Fixes: 0bdd2ed4138e ("sched: run_posix_cpu_timers: Don't check ->exit_state, use lock_task_sighand()") Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/time/posix-cpu-timers.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1374,6 +1374,15 @@ void run_posix_cpu_timers(void) lockdep_assert_irqs_disabled(); /* + * Ensure that release_task(tsk) can't happen while + * handle_posix_cpu_timers() is running. Otherwise, a concurrent + * posix_cpu_timer_del() may fail to lock_task_sighand(tsk) and + * miss timer->it.cpu.firing != 0. + */ + if (tsk->exit_state) + return; + + /* * If the actual expiry is deferred to task work context and the * work is already scheduled there is no point to do anything here. */