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Date: Thu, 8 Feb 2024 17:11:19 +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] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD
Message-ID: <20240208161118.GI19801@redhat.com>
References: <20240207114549.GA12697@redhat.com>
 <20240208-fragt-prospekt-7866333b15f0@brauner>
 <20240208135344.GD19801@redhat.com>
 <20240208143407.GF19801@redhat.com>
 <20240208-klopapier-aushebeln-446ac80a6e9b@brauner>
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On 02/08, Christian Brauner wrote:
>
> > Is prepare_kill_siginfo() correct when we send a signal to the child
> > pid namespace? si_pid = task_tgid_vnr(current) doesn't look right in
> > this case but perhaps I am totally confused.
> >
> > And why do we need it at all? Can't sys_kill() and pidfd_send_signal()
> > just use SEND_SIG_NOINFO?
>
> Yeah, good point. I don't remember as it's been quite a while ago. My
> guess is that it just tried to mirror kill() itself without being aware
> of SEND_SIG_NOINFO. If you don't find anything wrong with this then
> switch it to SEND_SIG_NOINFO in a preparatory patch we can backport,
> please.

Yes, but I still feel I must have missed something. Will read this code
tomorrow.

And another note for the record before I forget this. We can probably
improve and rename access_pidfd_pidns(). Currently it is only used by
pidfd_send_signal() but pidns_install() looks like another user.

Oleg.