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 705D8202C44 for ; Tue, 17 Jun 2025 14:47:47 +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=1750171667; cv=none; b=OvEcZIR0xkf0Dv2uDuevtbGvZJSadoB6EcnblUOnrM6xcJC+QFQ06Cw0Zm9M461Dkhdi0i9qGrdl2NHk1qDHrAleDbqb745s+1jW7zAn8vMlcFTtdvN7N1FzdVcVW5dEX/p1ksdCupHyz3ZlVkA2C56x2o8mBuiCRrYZJdvA32w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750171667; c=relaxed/simple; bh=OqlrAe7kpRdGM7wGJ+6dcTFlrN47sWpcIdSGsoGV0Ig=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=Kf0bwi2bgnkN9PNOdQ+yen71gtRaeQwmqHTJJllyd8rc/esz8gVGkmxkRd+x64/3IyaikF39lgoJ1onDUPv1GU+OAAH/LkBFdZ4cF3e69OgANv0eJSdKfQ0//A7J+UA9gPrQ4NpN6OAO7ialMahDAN362CrKn/scrl/cawY6qGg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XLPSz5uf; 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="XLPSz5uf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9954EC4CEE3; Tue, 17 Jun 2025 14:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750171667; bh=OqlrAe7kpRdGM7wGJ+6dcTFlrN47sWpcIdSGsoGV0Ig=; h=Subject:To:Cc:From:Date:From; b=XLPSz5ufIKdx9C6uZPTwU2UIoUDXI4EnLlDOWrU3Is2R/HkVTwlxKvbB7e8EYagD4 6obT1G55Zmdh2lK/GFVAVWFDTFgoBMT48hWhSW1U1Rnk9+4O8ZUH3YFb53NrSP/qzA GPcUmnpyxYTkclWhpZo33DYhKIGC7U+zoSWfFTOY= Subject: FAILED: patch "[PATCH] posix-cpu-timers: fix race between handle_posix_cpu_timers()" failed to apply to 5.4-stable tree To: oleg@redhat.com,bsevens@google.com,torvalds@linux-foundation.org Cc: From: Date: Tue, 17 Jun 2025 16:47:44 +0200 Message-ID: <2025061744-precinct-rubble-45c9@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x f90fff1e152dedf52b932240ebbd670d83330eca # git commit -s git send-email --to '' --in-reply-to '2025061744-precinct-rubble-45c9@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From f90fff1e152dedf52b932240ebbd670d83330eca Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 13 Jun 2025 19:26:50 +0200 Subject: [PATCH] posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 50e8d04ab661..2e5b89d7d866 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1405,6 +1405,15 @@ 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.