From patchwork Tue Sep 3 15:16:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13788897 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 D6C7B187FE6; Tue, 3 Sep 2024 15:15:45 +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=1725376545; cv=none; b=WLWqjNhebCuni3XrnNnEqMzKyHMvrX236MzBrt/6pU1imSkGTyLEAF3JprsgbtLCrTC4uKVmOkZfCSNfaam1/s1oDonFv39Fi7CVlH1VLkRsNhuv2fBrNcM8P8KferajUgYY3HBNkMDKQW7qf4gDvUu42MeuZ1aNMMvWr7Gfm6M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725376545; c=relaxed/simple; bh=JRNvkWKv8faeqN2SY77i/XC+Z7D24JG0Kox+HzqPLzY=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=l8RoabaHPNrsjaAL9zGANug9iB8o5sRx9X7oARV9xekyPLQa95hKQeHwzgwnJIwgwbsZTaB2ez462Pr3juWGekSH4zwACyArEZz8A/LuhRy2VzrrObQKdyh7BJzqjHFC6q7WTCcrjmw+3FWFh5L9sUrhZRFFEQdYP3Rns9ixXhE= 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 87882C4CEC4; Tue, 3 Sep 2024 15:15:44 +0000 (UTC) Date: Tue, 3 Sep 2024 11:16:42 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , jkacur@redhat.com, Tomas Glozar , "Luis Claudio R. Goncalves" Subject: [PATCH] tracing/timerlat: Only clear timer if a kthread exists Message-ID: <20240903111642.35292e70@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. 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) --- kernel/trace/trace_osnoise.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 97864f1bb227..f0af479ce1e8 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -265,6 +265,8 @@ static inline void tlat_var_reset(void) */ 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)); } } @@ -2587,7 +2589,8 @@ 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;