Messages in this thread | | | Subject | Re: [PATCH v1] trace: Fix race in trace_open and buffer resize call | From | Gaurav Kohli <> | Date | Mon, 5 Oct 2020 10:09:34 +0530 |
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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); > } > > /** >
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