linux-kernel - Re: [PATCH 2/2] fs: Limit sys_mount to only request filesystem modules.

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Message-ID: <CAGXu5j+ygnVMynwKHBzfaPT=vx4vCka5RcBpyX+BHvSMokV8ow@mail.gmail.com>
Date:	Tue, 5 Mar 2013 11:32:00 -0800
From:	Kees Cook <keescook@...gle.com>
To:	Kay Sievers <kay@...y.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Brad Spengler <spender@...ecurity.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	PaX Team <pageexec@...email.hu>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH 2/2] fs: Limit sys_mount to only request filesystem modules.

On Tue, Mar 5, 2013 at 11:06 AM, Kay Sievers <kay@...y.org> wrote:
> On Mon, Mar 4, 2013 at 8:51 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>> Modify the request_module to prefix the file system type with "fs-"
>> and add aliases to all of the filesystems that can be built as modules
>> to match.
>>
>> A common practice is to build all of the kernel code and leave code
>> that is not commonly needed as modules, with the result that many
>> users are exposed to any bug anywhere in the kernel.
>>
>> Looking for filesystems with a fs- prefix limits the pool of possible
>> modules that can be loaded by mount to just filesystems trivially
>> making things safer with no real cost.
>
> '-' is a commonly used part of a module name, and does not mix well
> with ramdom user provided names.
>
> We usually use ':' as the prefix separator for modaliases, when
> user-supplied strings are prefixed with the subsystem.
>
> I think it would be nicer to change that, and I'm sure some creative
> guy calls the next filesystem of the month fs-$something :)

The precedent is "-". "netdev-" "pf-net-" etc. Naming something
fs-$something is fine as long as it's actually a filesystem. :)

-Kees

-- 
Kees Cook
Chrome OS Security
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