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Date: Wed, 14 Feb 2024 13:36:56 +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: <20240214123655.GB16265@redhat.com>
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 <20240209155644.GD3282@redhat.com>
 <20240210-abfinden-beimessen-2dbfea59b0da@brauner>
 <20240210123033.GA27557@redhat.com>
 <20240210-dackel-getan-619c70fefa62@brauner>
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On 02/10, Oleg Nesterov wrote:
>
> On 02/10, Christian Brauner wrote:
> >
> > +	if (type == PIDFD_SIGNAL_PROCESS_GROUP)
> > +		ret = kill_pgrp_info(sig, &kinfo, pid);
>
> I guess you meant
>
> 	if (type == PIDTYPE_PGID)
>
> other than that,
>
> Reviewed-by: Oleg Nesterov <oleg@redhat.com>

Yes, but there is another thing I hadn't thought of...

sys_pidfd_send_signal() does

	/* Only allow sending arbitrary signals to yourself. */
	ret = -EPERM;
	if ((task_pid(current) != pid) &&
	    (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL))
		goto err;

and I am not sure that task_pid(current) == pid should allow
the "arbitrary signals" if PIDFD_SIGNAL_PROCESS_GROUP.

Perhaps

	/* Only allow sending arbitrary signals to yourself. */
	ret = -EPERM;
	if ((task_pid(current) != pid || type == PIDTYPE_PGID) &&
	    (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)
		goto err;

?

Oleg.