linux-kernel - [PATCH] tools lib traceevent: Do not reassign parg after collapse

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Date:	Wed, 11 May 2016 15:09:36 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH] tools lib traceevent: Do not reassign parg after
 collapse_tree()


At the end of process_filter(), collapse_tree() was changed to update the
parg parameter, but the reassignment after the call wasn't removed.
What happens is that the "current_op" gets modified and freed and parg
is assigned to the new allocated argument. But after the call to
collapse_tree(), parg is assigned again to the just freed "current_op",
and this causes the tool to crash.

current_op must also be assigned to NULL in case of error, otherwise it
will cause it to be free()ed twice.

Cc: Namhyung Kim <namhyung@...nel.org>
Cc: stable@...r.kernel.org # 3.14+
Fixes: 42d6194d133c ("tools lib traceevent: Refactor process_filter()")
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 tools/lib/traceevent/parse-filter.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
index 0144b3d1bb77..88cccea3ca99 100644
--- a/tools/lib/traceevent/parse-filter.c
+++ b/tools/lib/traceevent/parse-filter.c
@@ -1164,11 +1164,11 @@ process_filter(struct event_format *event, struct filter_arg **parg,
 		current_op = current_exp;
 
 	ret = collapse_tree(current_op, parg, error_str);
+	/* collapse_tree() may free current_op, and updates parg accordingly */
+	current_op = NULL;
 	if (ret < 0)
 		goto fail;
 
-	*parg = current_op;
-
 	free(token);
 	return 0;
 
-- 
1.8.3.1