From: Gaurav Kohli gkohli@codeaurora.org
commit bbeb97464eefc65f506084fd9f18f21653e01137 upstream.
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.
Take buffer lock to fix this.
Link: https://lkml.kernel.org/r/1601976833-24377-1-git-send-email-gkohli@codeauror...
Cc: stable@vger.kernel.org Fixes: b23d7a5f4a07a ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU") Signed-off-by: Gaurav Kohli gkohli@codeaurora.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/ring_buffer.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4866,6 +4866,9 @@ void ring_buffer_reset_cpu(struct trace_ 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_
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(struc 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(struc atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->resize_disabled); } + + mutex_unlock(&buffer->mutex); }
/**