From fc128e85cfc458cd975b28a0eefea79e857e2df7 Mon Sep 17 00:00:00 2001 From: Douglas Raillard Date: Tue, 18 Mar 2025 18:09:05 +0000 Subject: [PATCH] tracing: Ensure module defining synth event cannot be unloaded while tracing commit 21581dd4e7ff6c07d0ab577e3c32b13a74b31522 upstream. Currently, using synth_event_delete() will fail if the event is being used (tracing in progress), but that is normally done in the module exit function. At that stage, failing is problematic as returning a non-zero status means the module will become locked (impossible to unload or reload again). Instead, ensure the module exit function does not get called in the first place by increasing the module refcnt when the event is enabled. Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Fixes: 35ca5207c2d11 ("tracing: Add synthetic event command generation functions") Link: https://lore.kernel.org/20250318180906.226841-1-douglas.raillard@arm.com Signed-off-by: Douglas Raillard Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_synth.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 624e0867316d..28d15b023ad7 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -859,6 +859,34 @@ static struct trace_event_fields synth_event_fields_array[] = { {} }; +static int synth_event_reg(struct trace_event_call *call, + enum trace_reg type, void *data) +{ + struct synth_event *event = container_of(call, struct synth_event, call); + + switch (type) { + case TRACE_REG_REGISTER: + case TRACE_REG_PERF_REGISTER: + if (!try_module_get(event->mod)) + return -EBUSY; + break; + default: + break; + } + + int ret = trace_event_reg(call, type, data); + + switch (type) { + case TRACE_REG_UNREGISTER: + case TRACE_REG_PERF_UNREGISTER: + module_put(event->mod); + break; + default: + break; + } + return ret; +} + static int register_synth_event(struct synth_event *event) { struct trace_event_call *call = &event->call; @@ -888,7 +916,7 @@ static int register_synth_event(struct synth_event *event) goto out; } call->flags = TRACE_EVENT_FL_TRACEPOINT; - call->class->reg = trace_event_reg; + call->class->reg = synth_event_reg; call->class->probe = trace_event_raw_event_synth; call->data = event; call->tp = event->tp;