From: Gaurav Kohli <gkohli@codeaurora.org>
To: rostedt@goodmis.org, linux-kernel@vger.kernel.org
Cc: linux-arm-msm@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v1] trace: Fix race in trace_open and buffer resize call
Date: Mon, 5 Oct 2020 10:09:34 +0530 [thread overview]
Message-ID: <71b8fe4c-7be2-fe51-cd84-890320c98cda@codeaurora.org> (raw)
In-Reply-To: <1600955705-27382-1-git-send-email-gkohli@codeaurora.org>
Hi Steven,
please let us know, if below looks good to you or need modifications.
Thanks
Gaurav
On 9/24/2020 7:25 PM, Gaurav Kohli wrote:
> Below race can come, if trace_open and resize of
> cpu buffer is running parallely on different cpus
> CPUX CPUY
> ring_buffer_resize
> atomic_read(&buffer->resize_disabled)
> tracing_open
> tracing_reset_online_cpus
> ring_buffer_reset_cpu
> rb_reset_cpu
> rb_update_pages
> remove/insert pages
> resetting pointer
> This race can cause data abort or some times infinte loop in
> rb_remove_pages and rb_insert_pages while checking pages
> for sanity.
>
> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
> Cc: stable@vger.kernel.org
> ---
> Changes since v0:
> -Addressed Steven's review comments.
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 93ef0ab..15bf28b 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -4866,6 +4866,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
> if (!cpumask_test_cpu(cpu, buffer->cpumask))
> return;
>
> + /* prevent another thread from changing buffer sizes */
> + mutex_lock(&buffer->mutex);
> +
> atomic_inc(&cpu_buffer->resize_disabled);
> atomic_inc(&cpu_buffer->record_disabled);
>
> @@ -4876,6 +4879,8 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
>
> atomic_dec(&cpu_buffer->record_disabled);
> atomic_dec(&cpu_buffer->resize_disabled);
> +
> + mutex_unlock(&buffer->mutex);
> }
> EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
>
> @@ -4889,6 +4894,9 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
> struct ring_buffer_per_cpu *cpu_buffer;
> int cpu;
>
> + /* prevent another thread from changing buffer sizes */
> + mutex_lock(&buffer->mutex);
> +
> for_each_online_buffer_cpu(buffer, cpu) {
> cpu_buffer = buffer->buffers[cpu];
>
> @@ -4907,6 +4915,8 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
> atomic_dec(&cpu_buffer->record_disabled);
> atomic_dec(&cpu_buffer->resize_disabled);
> }
> +
> + mutex_unlock(&buffer->mutex);
> }
>
> /**
>
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2020-10-05 4:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 13:55 [PATCH v1] trace: Fix race in trace_open and buffer resize call Gaurav Kohli
2020-10-05 4:39 ` Gaurav Kohli [this message]
2020-10-05 14:25 ` Steven Rostedt
2020-10-05 14:27 ` Steven Rostedt
2020-10-05 16:29 ` Gaurav Kohli
2020-10-05 16:32 ` Steven Rostedt
2020-10-05 17:38 ` Gaurav Kohli
2020-10-06 9:33 Gaurav Kohli
2021-01-21 14:30 ` Denis Efremov
2021-01-21 19:09 ` Steven Rostedt
2021-01-21 20:15 ` Denis Efremov
2021-01-21 20:37 ` Steven Rostedt
2021-01-22 10:59 ` Greg KH
2021-01-22 11:25 ` Gaurav Kohli
2021-01-22 14:37 ` Steven Rostedt
2021-01-23 10:49 ` Denis Efremov
2021-01-23 16:33 ` Gaurav Kohli
2021-01-24 3:21 ` Steven Rostedt
2021-01-24 9:57 ` Gaurav Kohli
2021-01-24 10:05 ` Greg KH
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