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>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index e27bb6a..21d3475 100644 (file)
--- 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;