linux-kernel - Re: [RFC 2/2] initramfs with digital signature protection

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Message-ID: <20130207170542.GF6462@redhat.com>
Date:	Thu, 7 Feb 2013 12:05:43 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Dmitry Kasatkin <dmitry.kasatkin@...el.com>
Cc:	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/2] initramfs with digital signature protection

On Tue, Feb 05, 2013 at 02:34:50PM +0200, Dmitry Kasatkin wrote:

[..]
> +static int __init load_initramfs(void)
> +{
> +	static char *argv[] = { "pre-init", NULL, };
> +	extern char *envp_init[];
> +	int err;
> +
> +	/*
> +	 * In case that a resume from disk is carried out by linuxrc or one of
> +	 * its children, we need to tell the freezer not to wait for us.
> +	 */
> +	current->flags |= PF_FREEZER_SKIP;
> +
> +	err = call_usermodehelper_fns("/pre-init", argv, envp_init,
> +				      UMH_WAIT_PROC, init_init, init_cleanup,
> +				      NULL);
> +
> +	current->flags &= ~PF_FREEZER_SKIP;
> +
> +	pr_info("initramfs_sig /pre-init completed: %d\n", err);
> +

Dmitry, 

How do we make sure that this is the first call to user mode helpers. I
see that we first unpacked unsigned initramfs. Then after a while we 
unpacked signed initramfs on /root and did a chroot. But now there is
a window before chroot, where kernel might call into /sbin/hotplug or
/sbin/modprobe from unsigned initramfs?

Specifically, I put some printk and I am seeing calls to /sbin/hotplug
before we even unpacked signed initramfs.

Thanks
Vivek
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