Re: [PATCH v7 5/6] x86/signal: Detect and prevent an alternate signal stack overflow

[Borislav Petkov]

On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
> Nope.  on_sig_stack() is a horrible kludge and won't work here.  We
> could have something like __on_sig_stack() or sp_is_on_sig_stack() or
> something, though.

Yeah, see my other reply. Ack to either of those carved out helpers.

> I figure that the people whose programs spontaneously crash should get
> a hint why if they look at dmesg.  Maybe the message should say
> "overflowed sigaltstack -- try noavx512"?

I guess, as long as it is ratelimited. I mean, we can remove it later if
it starts gettin' annoying.

> We really ought to have a SIGSIGFAIL signal that's sent, double-fault
> style, when we fail to send a signal.

Yeap, we should be able to tell userspace that we couldn't send a
signal, hohumm.

Thx.

-- 
Regards/Gruss,
    Boris.

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