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

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Message-ID: <20240209-festmachen-gekreische-7616d41f6e43@brauner>
Date: Fri, 9 Feb 2024 12:29:50 +0100
From: Christian Brauner <brauner@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
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 Fri, Feb 09, 2024 at 11:28:17AM +0100, Oleg Nesterov wrote:
> On 02/08, Oleg Nesterov 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
> 
> Yes, but iiuc send_signal_locked() should fixup si_pid/si_uid, so it
> is not buggy.

It must've been. Yesterday I realized that otherwise kill(2) would have
been broken for a long time. I think this was originally fixed in commit
6588c1e3ff01 ("signals: SI_USER: Masquerade si_pid when crossing pid ns
boundary").