From: Donggeun Yoo <donggeunyoo.kernel@gmail.com> mainline inclusion from mainline-v7.3 commit a0777b9e53157f1f6848a0fd0650f5465391ea81 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/10312 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- In event_hist_trigger_parse() where it needs to create actions like "onmatch", it calls: event_hist_trigger_parse() { create_actions() { action_create() { trace_action_create() { trace_action_create_field_var() { create_field_var_hist() Where create_field_var_hist() does a loop on the hist_data representing the keys. The issue is, if the keys uses one of the pseudo field types (like common_cpu), the hist_data field element will have NULL for its field member causing a NULL pointer dereference when accessing the key_field->field->name. # echo 'hist:keys=common_cpu:ts0=common_timestamp.usecs' > \ events/sched/sched_waking/trigger # echo 'my_synth u64 lat; int prio' > synthetic_events # echo 'hist:keys=common_cpu:wakeup_lat=common_timestamp.usecs-$ts0:\ onmatch(sched.sched_waking).my_synth($wakeup_lat,prio)' > \ events/sched/sched_switch/trigger KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:create_field_var_hist+0x771/0x1380 Call Trace: trace_action_create_field_var+0x360/0x600 trace_action_create+0x393/0xe80 event_hist_trigger_parse+0x3e47/0x69e0 trigger_process_regex+0x1a6/0x250 event_trigger_write+0xce/0x160 Instead of accessing it directly, use the proper handler expr_field_str() to get the name. The three previous patches are prerequisites: without them a .buckets key and a common_stacktrace key each render into a command that cannot be parsed back. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260914053443.981201-5-donggeunyoo.kernel@gmail.co... Fixes: 02205a6752f2 ("tracing: Add support for 'field variables'") Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com> Assisted-by: Claude:claude-fable-5 Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Tengda Wu <wutengda2@huawei.com> --- 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 9af96b7aef67..6f5ec6ff4663 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -3053,7 +3053,7 @@ create_field_var_hist(struct hist_trigger_data *target_hist_data, key_field = hist_data->fields[i]; if (!first) seq_buf_putc(&s, ','); - seq_buf_puts(&s, key_field->field->name); + expr_field_str(key_field, &s); first = false; } -- 2.34.1