Re: [PATCH v8 5/6] x86/signal: Detect and prevent an alternate signal stack overflow

On May 11, 2021, at 11:36, Borislav Petkov [off-list ref] wrote:

I clumsily tried to register a SIGSEGV handler with

       act.sa_sigaction = my_sigsegv;
       sigaction(SIGSEGV, &act, NULL);

but that doesn't fire - task gets killed. Maybe I'm doing it wrong.

Since the altstack is already overflowed, perhaps set the flag like this -- not
using it to get the handler:

	act.sa_sigaction = my_sigsegv;
+	act.sa_flags = SA_SIGINFO;
	sigaction(SIGSEGV, &act, NULL);

FWIW, I think this is just a workaround for this case; in practice, altstack is
rather a backup for normal stack corruption.

Thanks,
Chang