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Date: Wed, 21 Feb 2024 13:55:26 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <brauner@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Tycho Andersen <tycho@tycho.pizza>, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect
 PIDFD_THREAD
Message-ID: <20240221125525.GA16773@redhat.com>
References: <20240216130625.GA8723@redhat.com>
 <20240216-ohnedies-improvisieren-58edcc102b6a@brauner>
 <20240216181214.GA10393@redhat.com>
 <20240220-einwurf-depesche-d8682be0370c@brauner>
 <20240220090255.GA7783@redhat.com>
 <20240220-pragmatisch-parzelle-8a1d10a94fae@brauner>
 <20240220110012.GB7783@redhat.com>
 <20240220-anlegen-feinmechaniker-3c2cfcc3ec01@brauner>
 <20240220162201.GD7783@redhat.com>
 <20240221-zapfhahn-pulsschlag-e8f9d919c350@brauner>
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On 02/21, Christian Brauner wrote:
>
> On Tue, Feb 20, 2024 at 05:22:02PM +0100, Oleg Nesterov wrote:
> >
> > > > > +       /* Currently unused. */
> > > > > +       if (info)
> > > > > +               return -EINVAL;
> > > >
> > > > Well, to me this looks like the unnecessary restriction... And why?
> > >
> > > Because right now we aren't sure that it's used
> >
> > Yes, but...
> >
> > > and we aren't sure what use-cases are there.
> >
> > the same use-cases as for rt_sigqueueinfo() ?
>
> Specifically for pidfd_send_signal() I mean. To me it seems very
> unlikely that anyone would be opening a pidfd to itself

Ah, with this, I do agree. And that is why (I think) we can remove
the "task_pid(current) != pid" check in the "info != NULL" branch.

Oleg.