tracing: Fix race in trace_open and buffer resize call (bbeb9746) · Commits · 戴 / test

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@codeaurora.org Cc: stable@vger.kernel.org Fixes: ("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>

kernel/trace/ring_buffer.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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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