linux-kernel - [RFC PATCH 15/16] PM / hibernate: Bypass verification logic on legacy BIOS

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Date:	Thu, 16 Jul 2015 22:25:29 +0800
From:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-efi@...r.kernel.org, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	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>,
	Jiri Kosina <jkosina@...e.cz>,
	"H. Peter Anvin" <hpa@...or.com>, "Lee, Chun-Yi" <jlee@...e.com>
Subject: [RFC PATCH 15/16] PM / hibernate: Bypass verification logic on legacy BIOS

Current hibernate signature verification solution relies on EFI stub
and efi boot service variable on x86 architecture. So the verification
logic was bypassed on legacy BIOS through checking EFI_BOOT flag.

Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
---
 drivers/firmware/efi/efi-hibernate_keys.c | 3 +++
 kernel/power/Kconfig                      | 3 ++-
 kernel/power/snapshot.c                   | 8 ++++++--
 kernel/power/user.c                       | 6 +++++-
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/efi/efi-hibernate_keys.c b/drivers/firmware/efi/efi-hibernate_keys.c
index 90ae912..f33bf70 100644
--- a/drivers/firmware/efi/efi-hibernate_keys.c
+++ b/drivers/firmware/efi/efi-hibernate_keys.c
@@ -21,6 +21,9 @@ void create_swsusp_key_regen_flag(void)
 	struct efivar_entry *entry = NULL;
 	int err = 0;
 
+	if (!efi_enabled(EFI_RUNTIME_SERVICES))
+		return;
+
 	if (!set_swsusp_key_regen_flag)
 		return;
 
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 7a64bda..5b04ab9 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -78,7 +78,8 @@ config HIBERNATE_VERIFICATION
 	  This option provides support for generating and verifying the
 	  signature of memory snapshot image by HMAC-SHA1. Current mechanism
 	  relies on UEFI secure boot environment, EFI stub generates HMAC
-	  key for hibernate verification.
+	  key for hibernate verification. So, the verification logic will be
+	  bypassed on legacy BIOS.
 
 config HIBERNATE_VERIFICATION_FORCE
 	bool "Require hibernate snapshot image to be validly signed"
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 3eda715..0d64c3a 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -29,6 +29,7 @@
 #include <linux/slab.h>
 #include <linux/compiler.h>
 #include <linux/ktime.h>
+#include <linux/efi.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -1469,8 +1470,11 @@ error_digest:
 forward_ret:
 	if (ret)
 		pr_warn("PM: Signature verifying failed: %d\n", ret);
-	/* forward check result when verifying pass or not enforce verifying */
-	if (!ret || !sigenforce) {
+	if (ret == -ENODEV && !efi_enabled(EFI_BOOT)) {
+		pr_warn("PM: Bypass verification on non-EFI machine\n");
+		ret = 0;
+	} else if (!ret || !sigenforce) {
+		/* forward check result when verifying pass or not enforce verifying */
 		snapshot_fill_sig_forward_info(ret);
 		ret = 0;
 	}
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 8bcb051..d7407ef 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -24,6 +24,7 @@
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/freezer.h>
+#include <linux/efi.h>
 
 #include <asm/uaccess.h>
 
@@ -390,7 +391,10 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		break;
 
 	case SNAPSHOT_REGENERATE_KEY:
-		set_swsusp_key_regen_flag = !!arg;
+		if (!efi_enabled(EFI_BOOT))
+			error = -ENODEV;
+		else
+			set_swsusp_key_regen_flag = !!arg;
 		break;
 
 	default:
-- 
1.8.4.5

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