trace_events_filter: Use rcu_assign_pointer() when setting ftrace_event_call->filter

BugLink: http://bugs.launchpad.net/bugs/902312

commit d3d9acf646679c1981032b0985b386d12fccc60c upstream.

ftrace_event_call->filter is sched RCU protected but didn't use
rcu_assign_pointer().  Use it.

TODO: Add proper __rcu annotation to call->filter and all its users.

-v2: Use RCU_INIT_POINTER() for %NULL clearing as suggested by Eric.

Link: http://lkml.kernel.org/r/20111123164949.GA29639@google.com

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 256764ecccd..bd3c6369f80 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1766,7 +1766,7 @@ static int replace_system_preds(struct event_subsystem *system,
                  * replace the filter for the call.
                  */
                 filter = call->filter;
-                call->filter = filter_item->filter;
+                rcu_assign_pointer(call->filter, filter_item->filter);
                 filter_item->filter = filter;
 
                 fail = false;
@@ -1821,7 +1821,7 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
                 filter = call->filter;
                 if (!filter)
                         goto out_unlock;
-                call->filter = NULL;
+                RCU_INIT_POINTER(call->filter, NULL);
                 /* Make sure the filter is not being used */
                 synchronize_sched();
                 __free_filter(filter);
@@ -1862,7 +1862,7 @@ out:
          * string
          */
         tmp = call->filter;
-        call->filter = filter;
+        rcu_assign_pointer(call->filter, filter);
         if (tmp) {
                 /* Make sure the call is done with the filter */
                 synchronize_sched();