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

[Borislav Petkov]

On Mon, Apr 12, 2021 at 10:30:23PM +0000, Bae, Chang Seok wrote:
> On Mar 26, 2021, at 03:30, Borislav Petkov <bp@xxxxxxxxx> wrote:
> > On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
> >> 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.
> 
> Hi Boris,
> 
> Let me clarify some details as preparing to include this in a revision.
> 
> So, IIUC, a number needs to be assigned for this new SIGFAIL. At a glance, not
> sure which one to pick there in signal.h -- 1-31 fully occupied and the rest
> for 33 different real-time signals.
> 
> Also, perhaps, force_sig(SIGFAIL) here, instead of return -1 -- to die with
> SIGSEGV.

I think this needs to be decided together with userspace people so that
they can act accordingly and whether it even makes sense to them.

Florian, any suggestions?

Subthread starts here:

https://lkml.kernel.org/r/CALCETrXQZuvJQrHDMst6PPgtJxaS_sPk2JhwMiMDNPunq45YFg@xxxxxxxxxxxxxx

Thx.

-- 
Regards/Gruss,
    Boris.

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