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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 29 Sep 2022 14:31:41 -0700
Message-ID: <CAHk-=wi2JKDawG44kpS-bbrATB6LDyRx64LwdXEzZk2RYwkzJg@mail.gmail.com>
Subject: Re: [PATCH 3/4] proc: Point /proc/net at /proc/thread-self/net
 instead of /proc/self/net
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     David Laight <David.Laight@aculab.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Serge E. Hallyn" <serge@hallyn.com>
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On Thu, Sep 29, 2022 at 2:27 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Put it another way:
>
> David:
>         when I'm opening /proc/net/whatever, I want its contents to match
>         this thread's netns, not that of some other thread.
> dhclient+apparmor:
>         whatever you get from /proc/net/dev, it would better be at
>         /proc/<pid>/net/dev, no matter which thread you happen to be.

... which actually creates an opening for a truly disgusting solution:

 - when an outsider else opens /proc/<pid>/net, they get the thread leader netns

 - when a thread opens its *own* thread group /proc/<pid>/net, it gets
its own thread netns, not the thread leader one.

Disgusting.

            Linus