linux-kernel - Re: [PATCH v4 2/5] pid: Add PIDFD_IOCTL_GETFD to fetch file descriptors from processes

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Message-ID: <CAMp4zn9R3XoV=xLi9y0vn-DotUQGRFA8Cp14aYYvkVYEUuW48w@mail.gmail.com>
Date:   Thu, 19 Dec 2019 21:21:23 -0800
From:   Sargun Dhillon <sargun@...gun.me>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Tycho Andersen <tycho@...ho.ws>, Jann Horn <jannh@...gle.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Gian-Carlo Pascutto <gpascutto@...illa.com>,
        Emilio Cobos Álvarez <ealvarez@...illa.com>,
        Florian Weimer <fweimer@...hat.com>,
        Jed Davis <jld@...illa.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 2/5] pid: Add PIDFD_IOCTL_GETFD to fetch file
 descriptors from processes

On Thu, Dec 19, 2019 at 5:43 PM Andy Lutomirski <luto@...nel.org> wrote:
>
>
> I don't think this is MODE_READ.  By copying an fd from the task, you
> can easily change its state.
Would PTRACE_MODE_ATTACH_REALCREDS  work? I'm curious what
kind of state change you can cause by borrowing an FD?


>
> IMO it would be really nice if pidfd could act more like a capability
> here and carry a ptrace mode, for example.  But I guess it doesn't
> right now.
>
>
> --Andy