Re: [PATCH resend 6/8] tracing/ftrace: Add might_fault check to syscall probes

[Thomas Gleixner]

On Mon, Sep 30 2024 at 15:23, Mathieu Desnoyers wrote:
> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
> index a3d8ac00793e..0430890cbb42 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -303,6 +303,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
>  	 * Syscall probe called with preemption enabled, but the ring
>  	 * buffer and per-cpu data require preemption to be disabled.
>  	 */
> +	might_fault();
>  	guard(preempt_notrace)();

I find it odd that the might_fault() check is in all the implementations
and not in the tracepoint itself:

    if (syscall) {
        might_fault();
 	rcu_read_unlock_trace();
   } else ...     

That's where I would have expected it to be.

Thanks,

        tglx