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[PATCH 2/2] tracing: Check keys for variable references in expressions too

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

There's an existing check for variable references in keys, but it
doesn't go far enough.  It checks whether a key field is a variable
reference but doesn't check whether it's an expression containing
variable references, which can cause the same problems for callers.

Use the existing field_has_hist_vars() function rather than a direct
top-level flag check to catch all possible variable references.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Reported-by: Vincent Bernat <vincent@xxxxxxxxx>
 kernel/trace/trace_events_hist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 3795207a48a0..bf993a9a65ec 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -3970,8 +3970,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			goto out;
-		if (hist_field->flags & HIST_FIELD_FL_VAR_REF) {
-			hist_err("Using variable references as keys not supported: ", field_str);
+		if (field_has_hist_vars(hist_field, 0))	{
+			hist_err("Using variable references in keys not supported: ", field_str);
 			destroy_hist_field(hist_field, 0);
 			ret = -EINVAL;
 			goto out;