linux-kernel - [PATCH 3.16 278/305] tracing: Fix memory leak in set_trigger

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Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        "Tom Zanussi" <tom.zanussi@...ux.intel.com>
Subject: [PATCH 3.16 278/305] tracing: Fix memory leak in set_trigger_filter()

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

commit 3cec638b3d793b7cacdec5b8072364b41caeb0e1 upstream.

When create_event_filter() fails in set_trigger_filter(), the filter may
still be allocated and needs to be freed. The caller expects the
data->filter to be updated with the new filter, even if the new filter
failed (we could add an error message by setting set_str parameter of
create_event_filter(), but that's another update).

But because the error would just exit, filter was left hanging and
nothing could free it.

Found by kmemleak detector.

Fixes: bac5fb97a173a ("tracing: Add and use generic set_trigger_filter() implementation")
Reviewed-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/trace/trace_events_trigger.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -727,8 +727,10 @@ static int set_trigger_filter(char *filt
 
 	/* The filter is for the 'trigger' event, not the triggered event */
 	ret = create_event_filter(file->event_call, filter_str, false, &filter);
-	if (ret)
-		goto out;
+	/*
+	 * If create_event_filter() fails, filter still needs to be freed.
+	 * Which the calling code will do with data->filter.
+	 */
  assign:
 	tmp = rcu_access_pointer(data->filter);