Re: [PATCH v2 1/2] signal: avoid shared siginfo namespace rewrites

[Oleg Nesterov <oleg@redhat.com>]

On 06/24, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@redhat.com> writes:
>
> > Add Eric.
> >
> > OK, I agree, it seems we need a simple fix.
> >
> > Acked-by: Oleg Nesterov <oleg@redhat.com>
> >
> > -------------------------------------------------------------------------
> > But let me add some "offtopic" notes... Why do we actually need this fix?
> >
> > kill_something_info(). But at first glance sys_kill/kill_something_info
> > can simply use SEND_SIG_NOINFO? If yes, this makes sense anyway, I will
> > re-check...

....

> So I think tracing the basic kill syscall is interesting.
>
> It uses an explicit siginfo.  It does that so it can choose
> between setting si_code to SI_TKILL and SI_USER.
>
> If the signal number is -1 it sends to every process in the
> system (or at least the pid namespace).
>
> That will require translation.

Most probably I was wrong, I didn't try to re-check yet.

But at first glance kill_something_info() never use SI_TKILL, and
__send_signal_locked(SEND_SIG_NOINFO) will do the necessary translation,
in this case si_pid/si_uid are the current task's pid/uid.

But again, I am not sure. Didn't have to to actually look at this code.

> I suspect just fixing send_signal_locked looks the easiest,
> especially if you make the siginfo parameter const.

Yes, agreed, and I have already acked this patch.

I think we can improve this unconditional rewrite later, on top of this fix.

Oleg.