tracing/events: fix concurrent access to ftrace_events list, fix

In filter_add_subsystem_pred() we should release event_mutex before
calling filter_free_subsystem_preds(), since both functions hold
event_mutex.

[ Impact: fix deadlock when writing invalid pred into subsystem filter ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: tzanussi@gmail.com
Cc: a.p.zijlstra@chello.nl
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
LKML-Reference: <4A028993.7020509@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 2 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8c62e5bdff09..85ad6a8939ad 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -636,14 +636,15 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
 
                 err = filter_add_pred(ps, call, pred);
                 if (err) {
+                        mutex_unlock(&event_mutex);
                         filter_free_subsystem_preds(system);
                         parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
-                        break;
+                        goto out;
                 }
                 replace_filter_string(call->filter, filter_string);
         }
         mutex_unlock(&event_mutex);
-
+out:
         return err;
 }