From: Christian Brauner <christian@brauner.io>
To: Andy Lutomirski <luto@kernel.org>
Cc: "Daniel Colascione" <dancol@google.com>,
"Jann Horn" <jannh@google.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Suren Baghdasaryan" <surenb@google.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Sultan Alsawaf" <sultan@kerneltoast.com>,
"Tim Murray" <timmurray@google.com>,
"Michal Hocko" <mhocko@kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Todd Kjos" <tkjos@android.com>,
"Martijn Coenen" <maco@android.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
"open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
kernel-team <kernel-team@android.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
"Kees Cook" <keescook@chromium.org>,
"Jonathan Kowalski" <bl0pbl33p@gmail.com>,
"Linux API" <linux-api@vger.kernel.org>
Subject: Re: pidfd design
Date: Tue, 26 Mar 2019 00:45:48 +0100 [thread overview]
Message-ID: <20190325234547.wo6lyimrp52qie5p@brauner.io> (raw)
In-Reply-To: <CALCETrV-52TXKbAim06Fr7vvFeOvk0SczneeV_Rtqr6-LN7-GQ@mail.gmail.com>
On Mon, Mar 25, 2019 at 04:42:14PM -0700, Andy Lutomirski wrote:
> On Mon, Mar 25, 2019 at 1:23 PM Daniel Colascione <dancol@google.com> wrote:
> >
> > On Mon, Mar 25, 2019 at 1:14 PM Jann Horn <jannh@google.com> wrote:
> > >
> > > On Mon, Mar 25, 2019 at 8:44 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> > > One ioctl on procfs roots to translate pidfds into that procfs,
> > > subject to both the normal lookup permission checks and only working
> > > if the pidfd has a translation into the procfs:
> > >
> > > int proc_root_fd = open("/proc", O_RDONLY);
> > > int proc_dir_fd = ioctl(proc_root_fd, PROC_PIDFD_TO_PROCFSFD, pidfd);
> > >
> > > And one ioctl on procfs directories to translate from PGIDs and PIDs to pidfds:
> > >
> > > int proc_pgid_fd = open("/proc/self", O_RDONLY);
> > > int self_pg_pidfd = ioctl(proc_pgid_fd, PROC_PROCFSFD_TO_PIDFD, 0);
> > > int proc_pid_fd = open("/proc/thread-self", O_RDONLY);
> > > int self_p_pidfd = ioctl(proc_pid_fd, PROC_PROCFSFD_TO_PIDFD, 0);
> > >
>
> This sounds okay to me. Or we could make it so that a procfs
> directory fd also works as a pidfd, but that seems more likely to be
> problematic than just allowing two-way translation like this
>
> > >
> > > And then, as you proposed, the new sys_clone() can just return a
> > > pidfd, and you can convert it into a procfs fd yourself if you want.
> >
> > I think that's the consensus we reached on the other thread. The
> > O_DIRECTORY open on /proc/self/fd/mypidfd seems like it'd work well
> > enough.
>
> I must have missed this particular email.
>
> IMO, if /proc/self/fd/mypidfd allows O_DIRECTORY open to work, then it
> really ought to do function just like /proc/self/fd/mypidfd/. and
> /proc/self/fd/mypidfd/status should work. And these latter two
> options seem nutty.
>
> Also, this O_DIRECTORY thing is missing the entire point of the ioctl
> interface -- it doesn't require procfs access.
The other option was to encode the pid in the callers pid namespace into
the pidfd's fdinfo so that you can parse it out and open /proc/<pid>.
You'd just need an event on the pidfd to tell you when the process has
died. Jonathan and I just discussed this.
next prev parent reply other threads:[~2019-03-25 23:45 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-10 20:34 [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android Sultan Alsawaf
2019-03-10 21:03 ` Greg Kroah-Hartman
2019-03-10 21:26 ` Sultan Alsawaf
2019-03-11 16:32 ` Joel Fernandes
2019-03-11 16:37 ` Joel Fernandes
2019-03-11 17:43 ` Michal Hocko
2019-03-11 17:58 ` Sultan Alsawaf
2019-03-11 20:10 ` Suren Baghdasaryan
2019-03-11 20:46 ` Sultan Alsawaf
2019-03-11 21:11 ` Joel Fernandes
2019-03-11 21:46 ` Sultan Alsawaf
2019-03-11 22:15 ` Suren Baghdasaryan
2019-03-11 22:36 ` Sultan Alsawaf
2019-03-12 8:05 ` Michal Hocko
2019-03-12 14:36 ` Suren Baghdasaryan
2019-03-12 15:25 ` Matthew Wilcox
2019-03-12 15:33 ` Michal Hocko
2019-03-12 15:39 ` Michal Hocko
2019-03-12 16:37 ` Sultan Alsawaf
2019-03-12 16:48 ` Michal Hocko
2019-03-12 16:58 ` Michal Hocko
2019-03-12 17:15 ` Suren Baghdasaryan
2019-03-12 17:17 ` Tim Murray
2019-03-12 17:45 ` Sultan Alsawaf
2019-03-12 18:43 ` Tim Murray
2019-03-12 18:50 ` Christian Brauner
2019-03-14 17:47 ` Joel Fernandes
2019-03-14 20:49 ` Sultan Alsawaf
2019-03-15 2:54 ` Joel Fernandes
2019-03-15 3:43 ` Sultan Alsawaf
2019-03-15 3:16 ` Steven Rostedt
2019-03-15 3:45 ` Sultan Alsawaf
2019-03-15 4:36 ` Daniel Colascione
2019-03-15 13:36 ` Joel Fernandes
2019-03-15 15:56 ` Suren Baghdasaryan
2019-03-15 16:12 ` Daniel Colascione
2019-03-15 16:43 ` Steven Rostedt
2019-03-15 17:17 ` Daniel Colascione
2019-03-15 18:03 ` Christian Brauner
2019-03-15 18:13 ` Joel Fernandes
2019-03-15 18:24 ` Christian Brauner
2019-03-15 18:49 ` Joel Fernandes
2019-03-16 17:31 ` Suren Baghdasaryan
2019-03-16 18:00 ` Daniel Colascione
2019-03-16 18:57 ` Christian Brauner
2019-03-16 19:37 ` Suren Baghdasaryan
2019-03-17 1:53 ` Joel Fernandes
2019-03-17 11:42 ` Christian Brauner
2019-03-17 15:40 ` Daniel Colascione
2019-03-18 0:29 ` Christian Brauner
2019-03-18 23:50 ` Joel Fernandes
2019-03-19 22:14 ` Christian Brauner
2019-03-19 22:26 ` Joel Fernandes
2019-03-19 22:48 ` Daniel Colascione
2019-03-19 23:10 ` Christian Brauner
2019-03-20 1:52 ` Joel Fernandes
2019-03-20 2:42 ` pidfd design Daniel Colascione
2019-03-20 3:59 ` Christian Brauner
2019-03-20 7:02 ` Daniel Colascione
2019-03-20 11:33 ` Joel Fernandes
2019-03-20 18:26 ` Christian Brauner
2019-03-20 18:38 ` Daniel Colascione
2019-03-20 18:51 ` Christian Brauner
2019-03-20 18:58 ` Andy Lutomirski
2019-03-20 19:14 ` Christian Brauner
2019-03-20 19:40 ` Daniel Colascione
2019-03-21 17:02 ` Andy Lutomirski
2019-03-25 20:13 ` Jann Horn
2019-03-25 20:23 ` Daniel Colascione
2019-03-25 23:42 ` Andy Lutomirski
2019-03-25 23:45 ` Christian Brauner [this message]
2019-03-26 0:00 ` Andy Lutomirski
2019-03-26 0:12 ` Christian Brauner
2019-03-26 0:24 ` Andy Lutomirski
2019-03-28 9:21 ` Christian Brauner
2019-03-20 19:19 ` Joel Fernandes
2019-03-20 19:29 ` Daniel Colascione
2019-03-24 14:44 ` Serge E. Hallyn
2019-03-24 18:48 ` Joel Fernandes
2019-03-20 19:11 ` Joel Fernandes
2019-05-07 2:16 ` [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android Sultan Alsawaf
2019-05-07 7:04 ` Greg Kroah-Hartman
2019-05-07 7:27 ` Sultan Alsawaf
2019-05-07 7:43 ` Greg Kroah-Hartman
2019-05-07 8:12 ` Sultan Alsawaf
2019-05-07 10:58 ` Christian Brauner
2019-05-07 16:28 ` Suren Baghdasaryan
2019-05-07 16:38 ` Christian Brauner
2019-05-07 16:53 ` Sultan Alsawaf
2019-05-07 20:01 ` Suren Baghdasaryan
2019-05-07 18:46 ` Joel Fernandes
2019-05-07 17:17 ` Sultan Alsawaf
2019-05-07 17:29 ` Greg Kroah-Hartman
2019-05-07 11:09 ` Greg Kroah-Hartman
2019-05-07 12:26 ` Michal Hocko
2019-05-07 15:31 ` Oleg Nesterov
2019-05-07 16:35 ` Sultan Alsawaf
2019-05-09 15:56 ` Oleg Nesterov
2019-05-09 18:33 ` Sultan Alsawaf
2019-05-10 15:10 ` Oleg Nesterov
2019-05-13 16:45 ` Sultan Alsawaf
2019-05-14 16:44 ` Steven Rostedt
2019-05-14 17:31 ` Sultan Alsawaf
2019-05-15 14:58 ` Oleg Nesterov
2019-05-15 17:27 ` Sultan Alsawaf
2019-05-15 18:32 ` Steven Rostedt
2019-05-15 18:52 ` Sultan Alsawaf
2019-05-15 20:09 ` Steven Rostedt
2019-05-16 13:54 ` Oleg Nesterov
2019-03-17 16:35 ` Serge E. Hallyn
2019-03-17 17:11 ` Daniel Colascione
2019-03-17 17:16 ` Serge E. Hallyn
2019-03-17 22:02 ` Suren Baghdasaryan
2019-03-20 20:07 pidfd design Alexey Dobriyan
2019-03-20 20:14 ` Daniel Colascione
2019-03-20 20:39 ` Alexey Dobriyan
2019-03-20 20:47 ` Christian Brauner
2019-03-20 20:50 ` Daniel Colascione
2019-03-20 21:00 ` Christian Brauner
2019-03-22 14:04 ` Michael Tirado
2019-03-25 17:45 ` Linus Torvalds
2019-03-25 16:14 ` Michael Tirado
2019-03-25 20:45 ` Christian Brauner
2019-03-25 18:50 ` Christian Brauner
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