| Message ID | 1600955705-27382-1-git-send-email-gkohli@codeaurora.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v1] trace: Fix race in trace_open and buffer resize call | expand |
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.
On Mon, 5 Oct 2020 10:09:34 +0530 Gaurav Kohli <gkohli@codeaurora.org> wrote: > Hi Steven, > > please let us know, if below looks good to you or need modifications. Strange, I don't have your original email in my inbox. I do have it in my LKML folder, but that's way too big for me to read. I checked my server logs. I found where I received this from LKML, but there's no log that I received this directly. How are you sending out your patches? If it doesn't land in my inbox, I'll never see it. -- Steve
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); } /**
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.