From: Martin Radev <martin.b.radev@gmail.com>
Date: Mon, 7 Sep 2020 15:16:13 +0200
Subject: x86/sev-es: Check required CPU features for SEV-ES
Git-commit: f5ed777586e08e09c4b6f1e87161a145ee1431cf
Patch-mainline: v5.10-rc1
References: jsc#SLE-14337
Make sure the machine supports RDRAND, otherwise there is no trusted
source of randomness in the system.
To also check this in the pre-decompression stage, make has_cpuflag()
not depend on CONFIG_RANDOMIZE_BASE anymore.
Signed-off-by: Martin Radev <martin.b.radev@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-73-joro@8bytes.org
---
arch/x86/boot/compressed/cpuflags.c | 4 ----
arch/x86/boot/compressed/misc.h | 5 +++--
arch/x86/boot/compressed/sev-es.c | 3 +++
arch/x86/kernel/sev-es-shared.c | 15 +++++++++++++++
arch/x86/kernel/sev-es.c | 3 +++
5 files changed, 24 insertions(+), 6 deletions(-)
--- a/arch/x86/boot/compressed/cpuflags.c
+++ b/arch/x86/boot/compressed/cpuflags.c
@@ -1,6 +1,4 @@
// SPDX-License-Identifier: GPL-2.0
-#ifdef CONFIG_RANDOMIZE_BASE
-
#include "../cpuflags.c"
bool has_cpuflag(int flag)
@@ -9,5 +7,3 @@ bool has_cpuflag(int flag)
return test_bit(flag, cpu.flags);
}
-
-#endif
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -85,8 +85,6 @@ void choose_random_location(unsigned lon
unsigned long *output,
unsigned long output_size,
unsigned long *virt_addr);
-/* cpuflags.c */
-bool has_cpuflag(int flag);
#else
static inline void choose_random_location(unsigned long input,
unsigned long input_size,
@@ -97,6 +95,9 @@ static inline void choose_random_locatio
}
#endif
+/* cpuflags.c */
+bool has_cpuflag(int flag);
+
#ifdef CONFIG_X86_64
extern int set_page_decrypted(unsigned long address);
extern int set_page_encrypted(unsigned long address);
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -145,6 +145,9 @@ void sev_es_shutdown_ghcb(void)
if (!boot_ghcb)
return;
+ if (!sev_es_check_cpu_features())
+ error("SEV-ES CPU Features missing.");
+
/*
* GHCB Page must be flushed from the cache and mapped encrypted again.
* Otherwise the running kernel will see strange cache effects when
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -9,6 +9,21 @@
* and is included directly into both code-bases.
*/
+#ifndef __BOOT_COMPRESSED
+#define error(v) pr_err(v)
+#define has_cpuflag(f) boot_cpu_has(f)
+#endif
+
+static bool __init sev_es_check_cpu_features(void)
+{
+ if (!has_cpuflag(X86_FEATURE_RDRAND)) {
+ error("RDRAND instruction not supported - no trusted source of randomness available\n");
+ return false;
+ }
+
+ return true;
+}
+
static void sev_es_terminate(unsigned int reason)
{
u64 val = GHCB_SEV_TERMINATE;
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -667,6 +667,9 @@ void __init sev_es_init_vc_handling(void
if (!sev_es_active())
return;
+ if (!sev_es_check_cpu_features())
+ panic("SEV-ES CPU Features missing");
+
/* Enable SEV-ES special handling */
static_branch_enable(&sev_es_enable_key);