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

On Mar 26, 2021, at 03:30, Borislav Petkov [off-list ref] wrote:

On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:

quoted

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.

Thanks,
Chang