Re: [PATCH v3 02/22] x86,mce: Delete ist_begin_non_atomic()

[Borislav Petkov]

On Wed, Feb 19, 2020 at 09:21:48AM -0800, Andy Lutomirski wrote:
> Unless there is a signal pending and the signal setup code is about to
> hit the same failed memory.  I suppose we can just treat cases like
> this as "oh well, time to kill the whole system".
>
> But we should genuinely agree that we're okay with deferring this handling.

Good catch!

static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
{

	...

		/* deal with pending signal delivery */
                if (cached_flags & _TIF_SIGPENDING)
                        do_signal(regs);

                if (cached_flags & _TIF_NOTIFY_RESUME) {
                        clear_thread_flag(TIF_NOTIFY_RESUME);
                        tracehook_notify_resume(regs);
                        rseq_handle_notify_resume(NULL, regs);
                }


Err, can we make task_work run before we handle signals? Or there's a
reason it is run in this order?

Comment over task_work_add() says:

 * This is like the signal handler which runs in kernel mode, but it doesn't
 * try to wake up the @task.

which sounds to me like this should really run before the signal
handlers...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette