linux-kernel - Re: [PATCH] afs: proc cells and rootcell are writeable

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Message-ID: <3099.1391126877@warthog.procyon.org.uk>
Date:	Fri, 31 Jan 2014 00:07:57 +0000
From:	David Howells <dhowells@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org,
	linux-afs@...ts.infradead.org,
	Pali Rohár <pali.rohar@...il.com>
Subject: Re: [PATCH] afs: proc cells and rootcell are writeable

Eric W. Biederman <ebiederm@...ssion.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@...romeda ~]# ls -l /proc/fs/afs/cells
	-r--r--r--. 1 root root 0 Jan 31 00:04 /proc/fs/afs/cells
	[root@...romeda ~]# echo add your-file-system.com 204.29.154.37 >/proc/fs/afs/cells
	[root@...romeda ~]# 

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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