linux-kernel - Re: [patch 00/13] devtmpfs patches

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Date:	Wed, 13 May 2009 15:34:49 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	David Howells <dhowells@...hat.com>
Cc:	Stephen Smalley <sds@...ho.nsa.gov>,
	"David P. Quigley" <dpquigl@...ho.nsa.gov>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Greg KH <gregkh@...e.de>, Jan Blunck <jblunck@...e.de>,
	James Morris <jmorris@...ei.org>,
	Eric Paris <eparis@...isplace.org>
Subject: Re: [patch 00/13] devtmpfs patches

On Wed, May 13, 2009 at 15:20, David Howells <dhowells@...hat.com> wrote:
> Kay Sievers <kay.sievers@...y.org> wrote:
>
>> +static struct cred *kern_cred;
>
> Can I suggest that you call your cred pointer dev_cred rather than kern_cred
> so that the naming is consistent with the other globals variables?

Sounds good.

>> +     kern_cred = prepare_kernel_cred(NULL);
>
> If you have no intention of altering the credentials you create, you might
> want to use &init_cred instead of kern_cred.  That said, you might want to
> allocate it and let the security module alter it before you use it.

Ah, didn't know that it was exported. It's the one in
include/linux/init_task.h, right? I'll give that a try.

> Also, Stephen is right, you should probably wrap all your accesses to the VFS
> in your devtmpfs credentials.  For instance, devtmpfs_create_node() calls
> vfs_mkdir() with the process's credentials via create_path() and directly with
> the kern_cred.
>
> What you probably want is:

>               nodename = device_get_nodename(dev, &tmp);
>               if (!nodename)
>                      return -ENOMEM;
>                curr_cred = override_creds(kern_cred);
...
>        out_name:
>                revert_creds(curr_cred);

Yeah, I have exactly that already now.

Thanks,
Kay
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