[PATCH] tracing: Reject .function on the function trace event

[David Carlier <devnexen@gmail.com>]

For the function event, parse_pred() handles the .function suffix
before the ftrace_event_is_function() case, so "ip.function == schedule"
builds a predicate with no regex. Setting it through perf then
dereferences the NULL pred->regex in ftrace_function_set_filter_pred().

The "ip" field of that event already takes a function name, so reject
the suffix there.

Fixes: e6745a4da964 ("tracing: Add a way to filter function addresses to function names")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 kernel/trace/trace_events_filter.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index c10951bcfc5f..11bb751c4388 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1743,6 +1743,12 @@ static int parse_pred(const char *str, void *data,
 	pred->op = op;
 
 	if (function) {
+		/* Function events already take a function name on 'ip' */
+		if (ftrace_event_is_function(call)) {
+			parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
+			goto err_free;
+		}
+
 		/* The field must be the same size as long */
 		if (field->size != sizeof(long)) {
 			parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
-- 
2.55.0