linux-kernel - [PATCH v2 15/16] PM / hibernate: Bypass verification logic on legacy BIOS

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Date:	Tue, 11 Aug 2015 14:16:35 +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@...ysocki.net>,
	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>, Ingo Molnar <mingo@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: [PATCH v2 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.

Reviewed-by: Jiri Kosina <jkosina@...e.com>
Tested-by: Jiri Kosina <jkosina@...e.com>
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 8a50bf1..2125302 100644
--- a/drivers/firmware/efi/efi-hibernate_keys.c
+++ b/drivers/firmware/efi/efi-hibernate_keys.c
@@ -17,6 +17,9 @@ void create_hibernation_key_regen_flag(void)
 	struct efivar_entry *entry = NULL;
 	int err = 0;
 
+	if (!efi_enabled(EFI_RUNTIME_SERVICES))
+		return;
+
 	if (!set_hibernation_key_regen_flag)
 		return;
 
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 1a03777..c30598e 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 486dd73..22b80b7 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 a183abd..686d095 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>
 
@@ -393,7 +394,10 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		break;
 
 	case SNAPSHOT_REGENERATE_KEY:
-		set_hibernation_key_regen_flag = !!arg;
+		if (!efi_enabled(EFI_BOOT))
+			error = -ENODEV;
+		else
+			set_hibernation_key_regen_flag = !!arg;
 		break;
 
 	default:
-- 
2.1.4

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