tracing: protect ring_buffer_expanded with trace_types_lock

Impact: prevent races with ring_buffer_expanded

This patch places the expanding of the tracing buffer under the
protection of the trace_types_lock mutex. It is highly unlikely
that there would be any contention, but better safe than sorry.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c61ee85c50bb..04ab8243a13d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2391,8 +2391,10 @@ int tracing_update_buffers(void)
 {
         int ret = 0;
 
+        mutex_lock(&trace_types_lock);
         if (!ring_buffer_expanded)
                 ret = tracing_resize_ring_buffer(trace_buf_size);
+        mutex_unlock(&trace_types_lock);
 
         return ret;
 }
@@ -2412,6 +2414,8 @@ static int tracing_set_tracer(const char *buf)
         struct tracer *t;
         int ret = 0;
 
+        mutex_lock(&trace_types_lock);
+
         if (!ring_buffer_expanded) {
                 ret = tracing_resize_ring_buffer(trace_buf_size);
                 if (ret < 0)
@@ -2419,7 +2423,6 @@ static int tracing_set_tracer(const char *buf)
                 ret = 0;
         }
 
-        mutex_lock(&trace_types_lock);
         for (t = trace_types; t; t = t->next) {
                 if (strcmp(t->name, buf) == 0)
                         break;