linux-kernel - Re: [RFC][PATCH] fs: Limit sys_mount to only loading filesystem modules.

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Date:	Sun, 3 Mar 2013 10:30:12 -0800
From:	Kees Cook <keescook@...gle.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"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>,
	Eric Paris <eparis@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [RFC][PATCH] fs: Limit sys_mount to only loading filesystem modules.

On Sun, Mar 3, 2013 at 2:14 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.
>
> Using aliases means user space can control the policy of which
> filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
> with blacklist and alias directives.  Allowing simple, safe,
> well understood work-arounds to known problematic software.
>
> This also addresses a rare but unfortunate problem where the filesystem
> name is not the same as it's module name and module auto-loading
> would not work.  While writing this patch I saw a handful of such
> cases.  The most significant being autofs that lives in the module
> autofs4.
>
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook
Chrome OS Security
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