tools lib traceevent: Do not reassign parg after collapse_tree()

commit 106b816cb46ebd87408b4ed99a2e16203114daa6 upstream.

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.

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

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Fixes: 42d6194d133c ("tools lib traceevent: Refactor process_filter()")
Link: http://lkml.kernel.org/r/20160511150936.678c18a1@gandalf.local.home
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
index b50234402fc2b368f39040a92ada39922f6464ee..15a43ee8e8b5c10608827163e4e1d04bf984ee8b 100644 (file)
--- a/tools/lib/traceevent/parse-filter.c
+++ b/tools/lib/traceevent/parse-filter.c
@@ -1163,11 +1163,11 @@ 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;
-
        return 0;
 
  fail_alloc: