Author: Gaurav Kohli <[email protected]>
backported upstream commit bbeb97464eefc65f506084fd9f18f21653e01137
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.
Signed-off-by: Gaurav Kohli <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
backport changes: ring_buffer_reset_cpu() fixed only
ring_buffer_reset_online_cpus() is not present in this kernel
https://jira.sw.ru/browse/PSBM-122343
Signed-off-by: Vasily Averin <[email protected]>
(cherry picked from vz7 commit d0b2f7cda662987572c5f84e7a8831d8c1135bd1)
Signed-off-by: Vasily Averin <[email protected]>
---
kernel/trace/ring_buffer.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index d7a0b16ec1fc..fb101b22b3d9 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4356,6 +4356,9 @@ 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);
@@ -4378,6 +4381,8 @@ 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);
--
2.25.1
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