linux-kernel - Re: [PATCH 11/18] Hibernate: introduced RSA key-pair to verify signature of snapshot

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Date:	Thu, 5 Sep 2013 09:53:48 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-crypto@...r.kernel.org,
	opensuse-kernel@...nsuse.org, David Howells <dhowells@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	James Bottomley <james.bottomley@...senpartnership.com>,
	Greg KH <gregkh@...uxfoundation.org>, JKosina@...e.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Gary Lin <GLin@...e.com>, Vivek Goyal <vgoyal@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>, Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH 11/18] Hibernate: introduced RSA key-pair to verify
 signature of snapshot

On Thu, 22 Aug, at 07:01:50PM, Lee, Chun-Yi wrote:
> +static int efi_status_to_err(efi_status_t status)
> +{
> +	int err;
> +
> +	switch (status) {
> +	case EFI_INVALID_PARAMETER:
> +		err = -EINVAL;
> +		break;
> +	case EFI_OUT_OF_RESOURCES:
> +		err = -ENOSPC;
> +		break;
> +	case EFI_DEVICE_ERROR:
> +		err = -EIO;
> +		break;
> +	case EFI_WRITE_PROTECTED:
> +		err = -EROFS;
> +		break;
> +	case EFI_SECURITY_VIOLATION:
> +		err = -EACCES;
> +		break;
> +	case EFI_NOT_FOUND:
> +		err = -ENODATA;
> +		break;
> +	default:
> +		err = -EINVAL;
> +	}
> +
> +	return err;
> +}

Please don't reimplement this. Instead make the existing function
global.

[...]

> +static void *load_wake_key_data(unsigned long *datasize)
> +{
> +	u32 attr;
> +	void *wkey_data;
> +	efi_status_t status;
> +
> +	if (!efi_enabled(EFI_RUNTIME_SERVICES))
> +		return ERR_PTR(-EPERM);
> +
> +	/* obtain the size */
> +	*datasize = 0;
> +	status = efi.get_variable(EFI_S4_WAKE_KEY_NAME, &EFI_HIBERNATE_GUID,
> +				  NULL, datasize, NULL);
> +	if (status != EFI_BUFFER_TOO_SMALL) {
> +		wkey_data = ERR_PTR(efi_status_to_err(status));
> +		pr_err("PM: Couldn't get wake key data size: 0x%lx\n", status);
> +		goto error;
> +	}

Is it safe to completely bypass the efivars interface and access
efi.get_variable() directly? I wouldn't have thought so, unless you can
guarantee that the kernel isn't going to access any of the EFI runtime
services while you execute this function.

-- 
Matt Fleming, Intel Open Source Technology Center
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