lkml.org 
[lkml]   [2020]   [Oct]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v1] trace: Fix race in trace_open and buffer resize call
From
Date
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.

\
 
 \ /
  Last update: 2020-10-05 06:40    [W:0.095 / U:0.600 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site