Re: [PATCH v2 5/7] linux: Remove SIGCANCEL/SIGSETXID handling on sigprocmask

[Florian Weimer <fweimer at redhat dot com>]

* Adhemerval Zanella:

> On 12/12/2019 09:54, Florian Weimer wrote:
>> * Adhemerval Zanella:
>> 
>>> The sigfillset already does it, and this is the canonical way to operate
>>> on sigset_t.  The only way to actually broke this assumption is if caller
>>> initialize sigset with memset or something similar, i.e, bypassing glibc
>>> (and again this is not a valid construction).
>> 
>> Is you argument that sigfillset already does this, and there is no way
>> to compute the complement of a signal set, so the bits for
>> SIGCANCEL and SIGSETXID can never become set?
>
> Yes.
>
>> 
>> I think it's possible to set them directly using sigaddset.  I don't see
>> why using SIGCANCEL/SIGSETXID with that function would be undefined.
>
> sigaddset filter out SIGCANCEL/SIGSETXID through __is_internal_signal, 
> returning EINVAL for such case.

Oh, I see.

It's still not clear to me whether it is not in fact better to allow
appplications to block internal signals (from a compatibility
perspective, e.g. if the application knows that the stack pointer is
problematic).

Thanks,
Florian