linux-kernel - Re: [PATCH] proc: make proc_fd

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Message-ID: <CA+55aFwAw=AZNqmDNip_P6WiY4zGRNWks-kLwN7ZgJ8JJsAx-A@mail.gmail.com>
Date:	Mon, 26 Aug 2013 12:35:26 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Willy Tarreau <w@....eu>, Al Viro <viro@...iv.linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] proc: make proc_fd_permission() thread-friendly

On Mon, Aug 26, 2013 at 11:09 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Patch looks ok to me, but since this has never worked and nobody has
> actually complained, I can't really convince myself that this is
> critical.

Actually, let's back-track..

Did you try the other approach? Make /proc/self point to the thread
instead of the task?

The thread-group leader seems to have these extra files:

 - autogroup, coredump_filter, mountstats, net, task

but quite frankly, at least "net" and "task" look like they should
exist there - with "task" pointing back to the actual task (it would
make more sense for "/proc/<pid>/task" itself to be named "threads",
but whatever).

Yes, it would be semantically different, but it would mean that
"/proc/self/fd/" would actually make sense in a way that it currently
does *not* - which would seem fairly important, since the primary use
for it tends to be /dev/stdin.

And the other semantic differences might be much harder to notice.
Worth testing?

                 Linus
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