Re: [RFC][PATCH 4/6][v3] Define siginfo_from_ancestor_ns()

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> writes:

>> I was going through the ->si_pid assignments to try and fix them at
>> source (like the mqueue patch I sent last week).
>
> OK.

Note.  When a signal goes to a process group (or similar) we can't fix
si_pid at the source.  We have to fix it when only a single destination
process is known.  It doesn't mean that fixing it at the source
is hopeless but...  

>> The two cases that don't fit the model are sys_kill() and sys_tkill().
>> For that I was hoping we could use siginfo_from_user() again. i.e
>>
>> 	if (siginfo_from_user())
>> 		masquerade_si_pid()
>>
>> in the default: case of send_signal(). To be safe, masquerade_si_pid()
>> could do it only iff si_code is either SI_USER or SI_TKILL.
>>
>> IOW, with some tweaks, I am trying to see if we can use siginfo_from_user()
>> in place of the SIG_FROM_USER.
>
> sys_rt_sigqueueinfo().
>
> But, perhaps we can just ignore the problems with sigqueueinfo() (and
> document them). 

Yes.  I don't think si_pid is valid in that case anyway.  It is the
kernel signals where si_pid is a reliable field that are important.

Eric