From 15911b869fe9855c9bf13ff43f183277f8bd2178 Mon Sep 17 00:00:00 2001 From: Gaurav Kohli Date: Thu, 3 Sep 2020 13:12:25 +0530 Subject: [PATCH] trace: Fix race in trace_open and buffer resize call 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 infine loop in rb_remove_pages and rb_insert_pages while checking pages for sanity. Take ring buffer lock in rb reset to avoid resetting of cpu buffer. Change-Id: I1d3344cca99e936d4e04a0e430e0ef9a975404c8 Signed-off-by: Gaurav Kohli --- kernel/trace/ring_buffer.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9a2581fe7ed5f..37d5050ca07b8 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4405,6 +4405,8 @@ void ring_buffer_reset_cpu(struct ring_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(&buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); @@ -4428,6 +4430,8 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&buffer->resize_disabled); + + mutex_unlock(&buffer->mutex); } EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);