tracing/events: Fix locking imbalance in the filter code

Américo Wang noticed that we have a locking imbalance in the
error paths of ftrace_profile_set_filter(), causing potential
leakage of event_mutex.

Also clean up other error codepaths related to event_mutex
while at it.

Plus fix an initialized variable in the subsystem filter code.

Reported-by: Américo Wang <xiyou.wangcong@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <2375c9f90910150247u5ccb8e2at58c764e385ffa490@mail.gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 11 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index e27bb6acc2dd..21d34757b955 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1230,10 +1230,10 @@ static int replace_system_preds(struct event_subsystem *system,
                                 struct filter_parse_state *ps,
                                 char *filter_string)
 {
+        struct event_filter *filter = system->filter;
         struct ftrace_event_call *call;
-        struct event_filter *filter;
-        int err;
         bool fail = true;
+        int err;
 
         list_for_each_entry(call, &ftrace_events, list) {
 
@@ -1262,7 +1262,7 @@ static int replace_system_preds(struct event_subsystem *system,
 
         if (fail) {
                 parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
-                return err;
+                return -EINVAL;
         }
         return 0;
 }
@@ -1281,8 +1281,7 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_disable_preds(call);
                 remove_filter_string(call->filter);
-                mutex_unlock(&event_mutex);
-                return 0;
+                goto out_unlock;
         }
 
         err = -ENOMEM;
@@ -1330,8 +1329,7 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_free_subsystem_preds(system);
                 remove_filter_string(system->filter);
-                mutex_unlock(&event_mutex);
-                return 0;
+                goto out_unlock;
         }
 
         err = -ENOMEM;
@@ -1386,15 +1384,20 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
                 if (call->id == event_id)
                         break;
         }
+
+        err = -EINVAL;
         if (!call)
-                return -EINVAL;
+                goto out_unlock;
 
+        err = -EEXIST;
         if (event->filter)
-                return -EEXIST;
+                goto out_unlock;
 
         filter = __alloc_preds();
-        if (IS_ERR(filter))
-                return PTR_ERR(filter);
+        if (IS_ERR(filter)) {
+                err = PTR_ERR(filter);
+                goto out_unlock;
+        }
 
         err = -ENOMEM;
         ps = kzalloc(sizeof(*ps), GFP_KERNEL);
@@ -1419,6 +1422,7 @@ free_preds:
         if (err)
                 __free_preds(filter);
 
+out_unlock:
         mutex_unlock(&event_mutex);
 
         return err;