[PATCH AUTOSEL for 4.9 086/100] tracing: Exclude 'generic fields' from histograms

[alexander . levin]

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

[ Upstream commit a15f7fc20389a8827d5859907568b201234d4b79 ]

There are a small number of 'generic fields' (comm/COMM/cpu/CPU) that
are found by trace_find_event_field() but are only meant for
filtering.  Specifically, they unlike normal fields, they have a size
of 0 and thus wreak havoc when used as a histogram key.

Exclude these (return -EINVAL) when used as histogram keys.

Link: http://lkml.kernel.org/r/956154cbc3e8a4f0633d619b886c97f0f0edf7b4.1506105045.git.tom.zanussi@xxxxxxxxxxxxxxx

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 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 f3a960ed75a1..0664044ade06 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -449,7 +449,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 	}
 
 	field = trace_find_event_field(file->event_call, field_name);
-	if (!field) {
+	if (!field || !field->size) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -547,7 +547,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 		}
 
 		field = trace_find_event_field(file->event_call, field_name);
-		if (!field) {
+		if (!field || !field->size) {
 			ret = -EINVAL;
 			goto out;
 		}
-- 
2.11.0