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From: Oleg Nesterov <oleg@redhat.com>
To: "Jürg Billeter" <j@bitron.ch>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Eric Biederman <ebiederm@xmission.com>,
	linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] prctl: add PR_[GS]ET_KILLABLE
Date: Wed, 1 Aug 2018 16:19:15 +0200
Message-ID: <20180801141914.GA21248@redhat.com> (raw)
In-Reply-To: <f21a22c9730ab455504f58a5fbda72cba0eb1227.camel@bitron.ch>

On 07/31, Jürg Billeter wrote:
>
> > Could you explain your use-case? Why a shell wants to use
> > CLONE_NEWPID?
>
> To guarantee that there won't be any runaway processes, i.e., ensure
> that no descendants (background helper daemons or misbehaving
> processes) survive when the child process is terminated.

We already have PR_SET_CHILD_SUBREAPER.

Perhaps we can finally add PR_KILL_MY_DESCENDANTS_ON_EXIT? This was already
discussed some time ago, but I can't find the previous discussion... Simple
to implement.

> And to prevent
> children from killing their ancestors.

OK, this is the only reason for CLONE_NEWPID which I can understand so far.
Not that I understand why this is that useful ;)

> > >  * As SIGSTOP is ignored when raised from the SIGNAL_UNKILLABLE process
> > >    itself, it's not possible to implement the stop action in a custom
> > >    SIGTSTP handler.
> >
> > Yes. So may be we actually want to change __isig() paths to use
> > SEND_SIG_FORCED (this is not that simple), or perhaps we can change
> > __send_signal() to not drop SIGSTOP sent to itself, or may be we can even
> > introduce SIG_DFL_EVEN_IF_INIT, I dunno.
>
> In my opinion, my patch is much simpler and also more general as it

Yes, yes, let me repeat that I am not arguing with your patch, I am just trying
to understand what

> > I can't understand this. An application should be changed anyway to do
> > PR_SET_KILLABLE?
>
> PR_SET_KILLABLE can be called (e.g., by the shell) between clone() and
> execve().

OK, this is true.

Oleg.


  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-30  7:52 [PATCH] " Jürg Billeter
2018-07-30 10:17 ` Oleg Nesterov
2018-07-30 19:32   ` Jürg Billeter
2018-07-30 19:39     ` Thomas Gleixner
2018-07-31  7:03 ` [PATCH v2] " Jürg Billeter
2018-07-31 14:39   ` Oleg Nesterov
2018-07-31 16:12     ` Jürg Billeter
2018-08-01 14:19       ` Oleg Nesterov [this message]
2018-08-03 10:15         ` Jürg Billeter
2018-08-03 12:14           ` Oleg Nesterov
2018-08-03 13:34           ` Eric W. Biederman
2018-08-03 14:39             ` Jürg Billeter
2018-07-31 16:26 ` [PATCH] " Jann Horn
2018-08-01  7:43   ` Jürg Billeter
2018-08-01  7:56     ` Jann Horn
2018-08-03 14:40 ` [PATCH v3 1/2] fork: do not rely on SIGNAL_UNKILLABLE for init check Jürg Billeter
2018-08-03 14:40   ` [PATCH v3 2/2] prctl: add PR_[GS]ET_KILLABLE Jürg Billeter
2018-09-06 22:42     ` Andrew Morton

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