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From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <christian@brauner.io>
Cc: jannh@google.com, viro@zeniv.linux.org.uk,
	torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
	arnd@arndb.de, dhowells@redhat.com, akpm@linux-foundation.org,
	cyphar@cyphar.com, ebiederm@xmission.com,
	elena.reshetova@intel.com, keescook@chromium.org,
	luto@amacapital.net, luto@kernel.org, tglx@linutronix.de,
	linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 1/2] pid: add pidfd_open()
Date: Wed, 15 May 2019 17:35:15 +0200
Message-ID: <20190515153515.GA20783@redhat.com> (raw)
In-Reply-To: <20190515143857.GB18892@redhat.com>

On 05/15, Oleg Nesterov wrote:
>
> On 05/15, Christian Brauner wrote:
> >
> > +SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
> > +{
> > +	int fd, ret;
> > +	struct pid *p;
> > +	struct task_struct *tsk;
> > +
> > +	if (flags)
> > +		return -EINVAL;
> > +
> > +	if (pid <= 0)
> > +		return -EINVAL;
> > +
> > +	p = find_get_pid(pid);
> > +	if (!p)
> > +		return -ESRCH;
> > +
> > +	rcu_read_lock();
> > +	tsk = pid_task(p, PIDTYPE_PID);
>
> You do not need find_get_pid() before rcu_lock and put_pid() at the end.
> You can just do find_vpid() under rcu_read_lock().

Ah, sorry. Somehow I forgot you need to call pidfd_create(pid), you can't
do this under rcu_read_lock().

So I was wrong, you can't avoid get/put_pid.

Oleg.


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-15 10:03 Christian Brauner
2019-05-15 10:04 ` [PATCH 2/2] tests: add pidfd_open() tests Christian Brauner
2019-05-15 12:29 ` [PATCH 1/2] pid: add pidfd_open() Geert Uytterhoeven
2019-05-15 14:00 ` Yann Droneaud
2019-05-15 14:16   ` Christian Brauner
2019-05-15 14:51     ` Aleksa Sarai
2019-05-15 15:29     ` Yann Droneaud
2019-05-15 14:38 ` Oleg Nesterov
2019-05-15 14:49   ` Christian Brauner
2019-05-15 15:19     ` Oleg Nesterov
2019-05-15 15:30       ` Christian Brauner
2019-05-15 15:35   ` Oleg Nesterov [this message]
2019-05-15 15:40     ` Christian Brauner
2019-05-15 17:45 ` Daniel Colascione
2019-05-16 13:08   ` Christian Brauner
2019-05-16 14:03     ` Jann Horn
2019-05-16 14:05       ` Christian Brauner
2019-05-16 14:53     ` Aleksa Sarai

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