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-zhengyej...
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 b8f1f0eadd2e..96d159af5194 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -6433,7 +6433,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops, /* Just return zero, not the number of registered triggers */ ret = 0; out: - if (ret == 0) + if (ret == 0 && glob[0]) hist_err_clear();
return ret;