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

From: Borislav Petkov
Date: Wed Feb 19 2020 - 12:42:34 EST

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)

if (cached_flags & _TIF_NOTIFY_RESUME) {
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