Re: [PATCH] consider stack access while checking for alternate signal stack

[Roland McGrath <roland@redhat.com>]

> >+#ifdef CONFIG_STACK_GROWSUP
> >+	return sp >= current->sas_ss_sp &&
> >+		sp - current->sas_ss_sp < current->sas_ss_size;
> 
> CONFIG_STACK_GROWSUP is wrong: If your stack grows up and sp ==
> sas_ss_sp + size than you are using the last entry in your sig stack
> which will be not recognized correctly. 

+		sp - current->sas_ss_sp <= current->sas_ss_size;

then?

> The case where sp == sas_ss_sp
> is also not detected correctly but this should not happen in real life.

So you say that sp==sas_ss_sp should not be considered "on the sig stack"?

> That is the PRE case which is the only relevant since we don't have any
> POST architectures. The check here produces the same results as my
> variant so it is okay :)
> So you prefer the smaller patch with comments around it?

Yes, I think it is far clearer and easier to read than what you posted.


Thanks,
Roland