[for-next][PATCH 4/4] ring-buffer: Add trace_recursive checks to ring_buffer_write()

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

The ring_buffer_write() function isn't protected by the trace recursive
writes. Luckily, this function is not used as much and is unlikely
to ever recurse. But it should still have the protection, because
even a call to ring_buffer_lock_reserve() could cause ring buffer
corruption if called when ring_buffer_write() is being used.

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/ring_buffer.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 1c037ad923db..6d6ebcea3463 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3013,9 +3013,12 @@ int ring_buffer_write(struct ring_buffer *buffer,
 	if (length > BUF_MAX_DATA_SIZE)
 		goto out;
 
+	if (unlikely(trace_recursive_lock(cpu_buffer)))
+		goto out;
+
 	event = rb_reserve_next_event(buffer, cpu_buffer, length);
 	if (!event)
-		goto out;
+		goto out_unlock;
 
 	body = rb_event_data(event);
 
@@ -3026,6 +3029,10 @@ int ring_buffer_write(struct ring_buffer *buffer,
 	rb_wakeups(buffer, cpu_buffer);
 
 	ret = 0;
+
+ out_unlock:
+	trace_recursive_unlock(cpu_buffer);
+
  out:
 	preempt_enable_notrace();
 
-- 
2.1.4


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