tracing: Fix rcu handling of event_trigger_data filter field

The filter field of the event_trigger_data structure is protected under
RCU sched locks. It was not annotated as such, and after doing so,
sparse pointed out several locations that required fix ups.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Tested-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 6 insertions, 4 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 0380cab0af9b..02b592f2d4b7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1057,7 +1057,7 @@ struct event_trigger_data {
         int                             ref;
         struct event_trigger_ops        *ops;
         struct event_command            *cmd_ops;
-        struct event_filter             *filter;
+        struct event_filter __rcu       *filter;
         char                            *filter_str;
         void                            *private_data;
         struct list_head                list;
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 12ac8a5d4d95..f6dd115b958d 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -67,6 +67,7 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
 {
         struct event_trigger_data *data;
         enum event_trigger_type tt = ETT_NONE;
+        struct event_filter *filter;
 
         if (list_empty(&file->triggers))
                 return tt;
@@ -76,7 +77,8 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
                         data->ops->func(data);
                         continue;
                 }
-                if (data->filter && !filter_match_preds(data->filter, rec))
+                filter = rcu_dereference(data->filter);
+                if (filter && !filter_match_preds(filter, rec))
                         continue;
                 if (data->cmd_ops->post_trigger) {
                         tt |= data->cmd_ops->trigger_type;
@@ -703,7 +705,7 @@ static int set_trigger_filter(char *filter_str,
         if (ret)
                 goto out;
  assign:
-        tmp = data->filter;
+        tmp = rcu_access_pointer(data->filter);
 
         rcu_assign_pointer(data->filter, filter);
 
@@ -719,7 +721,7 @@ static int set_trigger_filter(char *filter_str,
         if (filter_str) {
                 data->filter_str = kstrdup(filter_str, GFP_KERNEL);
                 if (!data->filter_str) {
-                        free_event_filter(data->filter);
+                        free_event_filter(rcu_access_pointer(data->filter));
                         data->filter = NULL;
                         ret = -ENOMEM;
                 }