From: Christian Brauner <christian@brauner.io>
To: Oleg Nesterov <oleg@redhat.com>
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 16:49:28 +0200 [thread overview]
Message-ID: <20190515144927.f2yxyi6w6lhn3xx7@brauner.io> (raw)
In-Reply-To: <20190515143857.GB18892@redhat.com>
On Wed, May 15, 2019 at 04:38:58PM +0200, 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().
Will do.
>
> > + if (!tsk)
> > + ret = -ESRCH;
> > + else if (unlikely(!thread_group_leader(tsk)))
> > + ret = -EINVAL;
>
> it seems that you can do a single check
>
> tsk = pid_task(p, PIDTYPE_TGID);
> if (!tsk)
> ret = -ESRCH;
>
> this even looks more correct if we race with exec changing the leader.
The logic here being that you can only reach the thread_group leader
from struct pid if PIDTYPE_PID == PIDTYPE_TGID for this struct pid?
Thanks, Oleg.
Christian
next prev parent reply other threads:[~2019-05-15 14:49 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-15 10:03 [PATCH 1/2] pid: add pidfd_open() 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 [this message]
2019-05-15 15:19 ` Oleg Nesterov
2019-05-15 15:30 ` Christian Brauner
2019-05-15 15:35 ` Oleg Nesterov
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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