linux-kernel - Re: [PATCH] pidfd: change pidfd_send_signal() to respect PIDFD

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Message-ID: <20240208161118.GI19801@redhat.com>
Date: Thu, 8 Feb 2024 17:11:19 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Christian Brauner <brauner@...nel.org>
Cc: Andy Lutomirski <luto@...capital.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tycho Andersen <tycho@...ho.pizza>, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD

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.