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Message-ID: <ac3eb2510905120854y7b44f608odf25af159fd6495c@mail.gmail.com>
Date: Tue, 12 May 2009 17:54:17 +0200
From: Kay Sievers <kay.sievers@...y.org>
To: Stephen Smalley <sds@...ho.nsa.gov>
Cc: "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>,
David Howells <dhowells@...hat.com>
Subject: Re: [patch 00/13] devtmpfs patches
On Tue, May 12, 2009 at 17:35, Stephen Smalley <sds@...ho.nsa.gov> wrote:
> I think the issue is that the devtmpfs functions are calling vfs helpers
> to create and unlink the device nodes, and those helpers apply
> permission checks based on the current process' credentials. I think a
> similar issue arose in sysfs a while ago. Options are to either bypass
> the vfs helpers to avoid that permission checking for what I think are
> intended to be kernel-internal operations, or to override credentials
> temporarily around the calls to the vfs helpers, ala:
> new_cred = prepare_kernel_cred(NULL);
> old_cred = override_creds(new_cred);
> rc = vfs_mknod(...);
> revert_creds(old_cred);
Ah, I see. That's probably what stuff like this is for:
/**
* lookup_one_noperm - bad hack for sysfs
* @name: pathname component to lookup
* @base: base directory to lookup from
*
* This is a variant of lookup_one_len that doesn't perform any permission
* checks. It's a horrible hack to work around the braindead sysfs
* architecture and should not be used anywhere else.
*
* DON'T USE THIS FUNCTION EVER, thanks.
*/
struct dentry *lookup_one_noperm(const char *name, struct dentry *base)
Thanks,
Kay
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