[PATCH 6.1 0746/1146] tracing/hist: Fix issue of losting command info in error_log

Greg Kroah-Hartman
2022-12-28T16:31:51Z

From: Zheng Yejian <zhengyejian1@huawei.com>

[ Upstream commit 608c6ed3337850c767ab0dd6c583477922233e29 ]

When input some constructed invalid 'trigger' command, command info
in 'error_log' are lost [1].

The root cause is that there is a path that event_hist_trigger_parse()
is recursely called once and 'last_cmd' which save origin command is
cleared, then later calling of hist_err() will no longer record origin
command info:

event_hist_trigger_parse() {
last_cmd_set() // <1> 'last_cmd' save origin command here at first
create_actions() {
onmatch_create() {
action_create() {
trace_action_create() {
trace_action_create_field_var() {
create_field_var_hist() {
event_hist_trigger_parse() { // <2> recursely called once
hist_err_clear() // <3> 'last_cmd' is cleared here
}
hist_err() // <4> No longer find origin command!!!

Since 'glob' is empty string while running into the recurse call, we
can trickly check it and bypass the call of hist_err_clear() to solve it.

[1]
# cd /sys/kernel/tracing
# echo "my_synth_event int v1; int v2; int v3;" >> synthetic_events
# echo 'hist:keys=pid' >> events/sched/sched_waking/trigger
# echo "hist:keys=next_pid:onmatch(sched.sched_waking).my_synth_event(\
pid,pid1)" >> events/sched/sched_switch/trigger
# cat error_log
[ 8.405018] hist:sched:sched_switch: error: Couldn't find synthetic event
Command:
hist:keys=next_pid:onmatch(sched.sched_waking).my_synth_event(pid,pid1)
^
[ 8.816902] hist:sched:sched_switch: error: Couldn't find field
Command:
hist:keys=next_pid:onmatch(sched.sched_waking).my_synth_event(pid,pid1)
^
[ 8.816902] hist:sched:sched_switch: error: Couldn't parse field variable
Command:
hist:keys=next_pid:onmatch(sched.sched_waking).my_synth_event(pid,pid1)
^
[ 8.999880] : error: Couldn't find field
Command:
^
[ 8.999880] : error: Couldn't parse field variable
Command:
^
[ 8.999880] : error: Couldn't find field
Command:
^
[ 8.999880] : error: Couldn't create histogram for field
Command:
^

Link: https://lore.kernel.org/linux-trace-kernel/20221207135326.3483216-1-zhengyejian1@huawei.com

Cc: <mhiramat@kernel.org>
Cc: <zanussi@kernel.org>
Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_events_hist.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1c82478e8dff..b6e5724a9ea3 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6438,7 +6438,7 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
if (se)
se->ref++;
out:
- if (ret == 0)
+ if (ret == 0 && glob[0])
hist_err_clear();

return ret;
--
2.35.1