From: Christian Brauner <christian.brauner@ubuntu.com>
To: Daniel Colascione <dancol@google.com>
Cc: Minchan Kim <minchan@kernel.org>,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Linux API <linux-api@vger.kernel.org>,
oleksandr@redhat.com, Suren Baghdasaryan <surenb@google.com>,
Tim Murray <timmurray@google.com>,
Sandeep Patil <sspatil@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
John Dias <joaodias@google.com>
Subject: Re: [PATCH 2/4] mm: introduce external memory hinting API
Date: Mon, 13 Jan 2020 21:42:37 +0100 [thread overview]
Message-ID: <20200113204237.ew6nn4ohxu7auw3u@wittgenstein> (raw)
In-Reply-To: <CAKOZuev5k3EquMd-6VbvruahjjtxQzRhUVo2ttgVyk+yYz9aOA@mail.gmail.com>
On Mon, Jan 13, 2020 at 11:27:03AM -0800, Daniel Colascione wrote:
> On Mon, Jan 13, 2020 at 11:10 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> > This does not
> > affect the permission checking you're performing here.
>
> Pidfds-as-capabilities sounds like a good change. Can you clarify what
> you mean here though? Do you mean that in order to perform some
> process-directed operation X on process Y, the pidfd passed to X must
> have been opened with PIDFD_CAP_X *and* the process *using* the pidfds
> must be able to perform operation X on process Y? Or do pidfds in this
> model "carry" permissions in the same way that an ordinary file
> descriptor "carries" the ability to write to a file if it was opened
> with O_WRONLY even if the FD is passed to a process that couldn't
> otherwise write to that file? Right now, pidfds are identity-only and
> always rely on the caller's permissions. I like the capability bit
> model because it makes pidfds more consistent with other file
> descriptors and enabled delegation of capabilities across the system.
I'm going back and forth on this. My initial implementation has it that
you'd need both, PIDFD_FLAG/CAP_X and the process using the pidfd must
be able to perform the operation X on process Y. The alternative becomes
tricky for e.g. anything that requires ptrace_may_access() permissions
such as getting an fd out from another task based on its pidfd and so
on.
Christian
next prev parent reply other threads:[~2020-01-13 20:42 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 21:34 [PATCH 0/4] introduce memory hinting API for external process Minchan Kim
2020-01-10 21:34 ` [PATCH 1/4] mm: factor out madvise's core functionality Minchan Kim
2020-01-11 7:37 ` SeongJae Park
2020-01-13 18:11 ` Minchan Kim
2020-01-13 18:22 ` SeongJae Park
2020-01-10 21:34 ` [PATCH 2/4] mm: introduce external memory hinting API Minchan Kim
2020-01-11 7:34 ` SeongJae Park
2020-01-13 18:02 ` Minchan Kim
2020-01-13 8:47 ` Kirill Tkhai
2020-01-13 10:42 ` Christian Brauner
2020-01-13 18:44 ` Minchan Kim
2020-01-13 19:10 ` Christian Brauner
2020-01-13 19:27 ` Daniel Colascione
2020-01-13 20:42 ` Christian Brauner [this message]
2020-01-13 21:04 ` Daniel Colascione
2020-01-14 19:20 ` Christian Brauner
2020-01-14 18:59 ` Minchan Kim
2020-01-14 19:22 ` Christian Brauner
2020-01-13 18:39 ` Minchan Kim
2020-01-13 19:18 ` Daniel Colascione
2020-01-14 8:39 ` Kirill Tkhai
2020-01-14 19:12 ` Minchan Kim
2020-01-15 9:38 ` Kirill Tkhai
2020-01-10 21:34 ` [PATCH 3/4] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-01-10 21:34 ` [PATCH 4/4] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-01-11 7:42 ` SeongJae Park
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200113204237.ew6nn4ohxu7auw3u@wittgenstein \
--to=christian.brauner@ubuntu.com \
--cc=akpm@linux-foundation.org \
--cc=bgeffon@google.com \
--cc=dancol@google.com \
--cc=hannes@cmpxchg.org \
--cc=joaodias@google.com \
--cc=ktkhai@virtuozzo.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=minchan@kernel.org \
--cc=oleksandr@redhat.com \
--cc=shakeelb@google.com \
--cc=sonnyrao@google.com \
--cc=sspatil@google.com \
--cc=surenb@google.com \
--cc=timmurray@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).