5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Steven Rostedt rostedt@goodmis.org
[ Upstream commit b5e8acc14dcb314a9b61ff19dcd9fdd0d88f70df ]
When a module is loaded, it adds trace events defined by the module. It may also need to modify the modules trace printk formats to replace enum names with their values.
If two modules are loaded at the same time, the adding of the event to the ftrace_events list can corrupt the walking of the list in the code that is modifying the printk format strings and crash the kernel.
The addition of the event should take the trace_event_sem for write while it adds the new event.
Also add a lockdep_assert_held() on that semaphore in __trace_add_event_dirs() as it iterates the list.
Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org Link: https://lore.kernel.org/20250718223158.799bfc0c@batman.local.home Reported-by: Fusheng Huang(黄富生) Fusheng.Huang@luxshare-ict.com Closes: https://lore.kernel.org/all/20250717105007.46ccd18f@batman.local.home/ Fixes: 110bf2b764eb6 ("tracing: add protection around module events unload") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace_events.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2109,7 +2109,10 @@ __register_event(struct trace_event_call if (ret < 0) return ret;
+ down_write(&trace_event_sem); list_add(&call->list, &ftrace_events); + up_write(&trace_event_sem); + call->mod = mod;
return 0; @@ -2489,6 +2492,8 @@ __trace_add_event_dirs(struct trace_arra struct trace_event_call *call; int ret;
+ lockdep_assert_held(&trace_event_sem); + list_for_each_entry(call, &ftrace_events, list) { ret = __trace_add_new_event(call, tr); if (ret < 0)