From patchwork Thu Sep 5 12:53:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13792318 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 4F77617C990; Thu, 5 Sep 2024 12:52:29 +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=1725540749; cv=none; b=T8qPH4ZYF2ySvQjllucXsfpiNCUbFbBYdqKrEeT77RPr6hpQWGJtL9YgkTPiF1NFohoDwj4VGr+4MtodpX0MqtxvBVWonKnCLav58zshxxXH3BqTYMk5pHc58OOCnSeEsocI77xjf0SPphQKwSE+QcxSB1bfXIopdCx939oxu+0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725540749; c=relaxed/simple; bh=tN28YwSlwQtG46KzjQc8IJ4igXiJsYG+1FA/9ItvSmA=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=eyxQRhnK9AjDPj262iC/HL5jBjfUD+BewXad69XcEKTDKldAJT5XxW2J53wKfE02dheK6OFCPRBogk1umrOWpb20xZ3/ULV3R1jzgV3gAPFqA4A3QFHxvQsroEePVK8VIAIWSKGu6YVLVLmCOTRcHtrg3+FmY99dAoeCzKe4ykk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 230CDC4CEC3; Thu, 5 Sep 2024 12:52:28 +0000 (UTC) Date: Thu, 5 Sep 2024 08:53:30 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , "Luis Claudio R. Goncalves" , Tomas Glozar Subject: [PATCH v2] tracing/timerlat: Only clear timer if a kthread exists Message-ID: <20240905085330.45985730@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Steven Rostedt The timerlat tracer can use user space threads to check for osnoise and timer latency. If the program using this is killed via a SIGTERM, the threads are shutdown one at a time and another tracing instance can start up resetting the threads before they are fully closed. That causes the hrtimer assigned to the kthread to be shutdown and freed twice when the dying thread finally closes the file descriptors, causing a use-after-free bug. Only cancel the hrtimer if the associated thread is still around. Also add the interface_lock around the resetting of the tlat_var->kthread. Note, this is just a quick fix that can be backported to stable. A real fix is to have a better synchronization between the shutdown of old threads and the starting of new ones. Link: https://lore.kernel.org/all/20240820130001.124768-1-tglozar@redhat.com/ Cc: stable@vger.kernel.org Fixes: e88ed227f639e ("tracing/timerlat: Add user-space interface") Reported-by: Tomas Glozar Signed-off-by: Steven Rostedt (Google) --- Changes since v1: https://lore.kernel.org/20240903111642.35292e70@gandalf.local.home - Added taking the interface_lock around the tlat_var_reset code. kernel/trace/trace_osnoise.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 66a871553d4a..fc227a386077 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -252,6 +252,11 @@ static inline struct timerlat_variables *this_cpu_tmr_var(void) return this_cpu_ptr(&per_cpu_timerlat_var); } +/* + * Protect the interface. + */ +static struct mutex interface_lock; + /* * tlat_var_reset - Reset the values of the given timerlat_variables */ @@ -259,14 +264,20 @@ static inline void tlat_var_reset(void) { struct timerlat_variables *tlat_var; int cpu; + + /* Synchronize with the timerlat interfaces */ + mutex_lock(&interface_lock); /* * So far, all the values are initialized as 0, so * zeroing the structure is perfect. */ for_each_cpu(cpu, cpu_online_mask) { tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu); + if (tlat_var->kthread) + hrtimer_cancel(&tlat_var->timer); memset(tlat_var, 0, sizeof(*tlat_var)); } + mutex_unlock(&interface_lock); } #else /* CONFIG_TIMERLAT_TRACER */ #define tlat_var_reset() do {} while (0) @@ -331,11 +342,6 @@ struct timerlat_sample { }; #endif -/* - * Protect the interface. - */ -static struct mutex interface_lock; - /* * Tracer data. */ @@ -2579,7 +2585,8 @@ static int timerlat_fd_release(struct inode *inode, struct file *file) osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu); tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu); - hrtimer_cancel(&tlat_var->timer); + if (tlat_var->kthread) + hrtimer_cancel(&tlat_var->timer); memset(tlat_var, 0, sizeof(*tlat_var)); osn_var->sampling = 0;