[PATCH v3] tools lib traceevent: add checks for returned EVENT_ERROR type

[Dean Nelson <dnelson@redhat.com>]

Running the following perf-stat command on an arm64 system produces the
following result...

  [root@aarch64 ~]# perf stat -e kmem:mm_page_alloc -a sleep 1
    Warning: [kmem:mm_page_alloc] function sizeof not defined
    Warning: Error: expected type 4 but read 0
  Segmentation fault
  [root@aarch64 ~]#

The second warning message and SIGSEGV stem from the issue expressed in the
first warning message, and are the result of ignoring the EVENT_ERROR type
returned back through the call chain.

Dealing with the first warning message is beyond the scope of this patch. But
the second warning is addressed by this patch's first hunk. And the SIGSEGV is
eliminated by its second hunk.

Signed-off-by: Dean Nelson <dnelson@redhat.com>
---
Changes in v3:
  - The desire was that a goto be used, not what I'd done in v2.

Changes in v2:
  - Moved the second hunk's check for EVENT_ERROR to a separate line.

 tools/lib/traceevent/event-parse.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index cc25f05..ed765a9 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -1680,6 +1680,9 @@ process_cond(struct event_format *event, struct print_arg *top, char **tok)
 	type = process_arg(event, left, &token);
 
  again:
+	if (type == EVENT_ERROR)
+		goto out_free;
+
 	/* Handle other operations in the arguments */
 	if (type == EVENT_OP && strcmp(token, ":") != 0) {
 		type = process_op(event, left, &token);
@@ -1939,6 +1942,12 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 			goto out_warn_free;
 
 		type = process_arg_token(event, right, tok, type);
+		if (type == EVENT_ERROR) {
+			free_arg(right);
+			/* token was freed in process_arg_token() via *tok */
+			token = NULL;
+			goto out_free;
+		}
 
 		if (right->type == PRINT_OP &&
 		    get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {