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x86-64: detect processors subject to AMD erratum #121 and refuse to boot
Processors with this erratum are subject to a DoS attack by unprivileged
guest users.
This is XSA-9 / CVE-2006-0744.
Signed-off-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -32,6 +32,9 @@
static char opt_famrev[14];
string_param("cpuid_mask_cpu", opt_famrev);
+static int opt_allow_unsafe;
+boolean_param("allow_unsafe", opt_allow_unsafe);
+
static inline void wrmsr_amd(unsigned int index, unsigned int lo,
unsigned int hi)
{
@@ -620,6 +623,11 @@ static void __devinit init_amd(struct cp
clear_bit(X86_FEATURE_MCE, c->x86_capability);
#ifdef __x86_64__
+ if (cpu_has_amd_erratum(c, AMD_ERRATUM_121) && !opt_allow_unsafe)
+ panic("Xen will not boot on this CPU for security reasons.\n"
+ "Pass \"allow_unsafe\" if you're trusting all your"
+ " (PV) guest kernels.\n");
+
/* AMD CPUs do not support SYSENTER outside of legacy mode. */
clear_bit(X86_FEATURE_SEP, c->x86_capability);
--- a/xen/include/asm-x86/amd.h
+++ b/xen/include/asm-x86/amd.h
@@ -127,6 +127,9 @@
#define AMD_MODEL_RANGE_START(range) (((range) >> 12) & 0xfff)
#define AMD_MODEL_RANGE_END(range) ((range) & 0xfff)
+#define AMD_ERRATUM_121 \
+ AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x0f, 0x0, 0x0, 0x3f, 0xf))
+
#define AMD_ERRATUM_170 \
AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x0f, 0x0, 0x0, 0x67, 0xf))
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