tracing/filters: clean up filter_add_subsystem_pred()

Impact: cleanup, memory leak fix

This patch cleans up filter_add_subsystem_pred():

- searches for the field before creating a copy of the pred

- fixes memory leak in the case a predicate isn't applied

- if -ENOMEM, makes sure there's no longer a reference to the
  pred so the caller can free the half-finished filter

- changes the confusing i == MAX_FILTER_PRED - 1 comparison
  previously remarked upon

This affects only per-subsystem event filtering.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237796808.7527.40.camel@charm-linux>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 25 insertions, 7 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 19f61dd23219..fdab30d6c835 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -585,6 +585,7 @@ subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
         }
 
         if (filter_add_subsystem_pred(system, pred)) {
+                filter_free_subsystem_preds(system);
                 filter_free_pred(pred);
                 return -EINVAL;
         }
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index fd01d8022ad1..4117c2ebc245 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -318,22 +318,39 @@ int filter_add_subsystem_pred(struct event_subsystem *system,
                         system->preds[i] = pred;
                         break;
                 }
-                if (i == MAX_FILTER_PRED - 1)
-                        return -EINVAL;
         }
 
+        if (i == MAX_FILTER_PRED)
+                return -EINVAL;
+
         events_for_each(call) {
+                int err;
+
                 if (!call->name || !call->regfunc)
                         continue;
 
-                if (!strcmp(call->system, system->name)) {
-                        event_pred = copy_pred(pred);
-                        if (event_pred)
-                                filter_add_pred(call, event_pred);
-                }
+                if (strcmp(call->system, system->name))
+                        continue;
+
+                if (!find_event_field(call, pred->field_name))
+                        continue;
+
+                event_pred = copy_pred(pred);
+                if (!event_pred)
+                        goto oom;
+
+                err = filter_add_pred(call, event_pred);
+                if (err)
+                        filter_free_pred(event_pred);
+                if (err == -ENOMEM)
+                        goto oom;
         }
 
         return 0;
+
+oom:
+        system->preds[i] = NULL;
+        return -ENOMEM;
 }
 
 int filter_parse(char **pbuf, struct filter_pred *pred)