From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Date: Wed, 27 May 2015 14:48:56 +0000 (-0400)
Subject: ring-buffer: Add trace_recursive checks to ring_buffer_write()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=985e871b28fc3e73ccd21cb999ce61266dc8c941;p=linux.git

ring-buffer: Add trace_recursive checks to ring_buffer_write()

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@goodmis.org>
---

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 1c037ad923db2..6d6ebcea3463c 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();