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From: David Howells <dhowells@redhat.com>
In-Reply-To: <8761p1m98f.fsf@xmission.com>
References: <8761p1m98f.fsf@xmission.com> <20140126122729.32113.19659.stgit@warthog.procyon.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc: dhowells@redhat.com, linux-kernel@vger.kernel.org,
        linux-afs@lists.infradead.org,
        Pali =?utf-8?Q?Roh=C3=A1r?= <pali.rohar@gmail.com>
Subject: Re: [PATCH] afs: proc cells and rootcell are writeable
Date: Fri, 31 Jan 2014 00:07:57 +0000
Message-ID: <3099.1391126877@warthog.procyon.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

Eric W. Biederman <ebiederm@xmission.com> wrote:

> These files have been read-only since this code was merged in 2002.
> Over a decade of not being used seems like a strong indication that no
> one cares about the write path.

Actually, things aren't as simple as they seem.  Without the patch applied:

	[root@andromeda ~]# ls -l /proc/fs/afs/cells
	-r--r--r--. 1 root root 0 Jan 31 00:04 /proc/fs/afs/cells
	[root@andromeda ~]# echo add your-file-system.com 204.29.154.37 >/proc/fs/afs/cells
	[root@andromeda ~]# 

You'll observe there is no error reported on the echo command.

Further, looking in dmesg, I see:

	kAFS: Added new cell 'your-file-system.com'

So the file *is* writable, *despite* i_mode.

David
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