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authorAndy Lutomirski <luto@amacapital.net>2014-12-05 19:03:28 -0800
committerBen Hutchings <ben@decadent.org.uk>2015-01-01 01:27:50 +0000
commit060d11323f35afb752a7ba6c5bead732c204de55 (patch)
tree46d5415faf86682dd338319411ae212563f2e05d /arch/x86
parent2f67670174ad4bd1c48e8b97cc107e3232d422ce (diff)
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x86, kvm: Clear paravirt_enabled on KVM guests for espfix32's benefit
commit 29fa6825463c97e5157284db80107d1bfac5d77b upstream. paravirt_enabled has the following effects: - Disables the F00F bug workaround warning. There is no F00F bug workaround any more because Linux's standard IDT handling already works around the F00F bug, but the warning still exists. This is only cosmetic, and, in any event, there is no such thing as KVM on a CPU with the F00F bug. - Disables 32-bit APM BIOS detection. On a KVM paravirt system, there should be no APM BIOS anyway. - Disables tboot. I think that the tboot code should check the CPUID hypervisor bit directly if it matters. - paravirt_enabled disables espfix32. espfix32 should *not* be disabled under KVM paravirt. The last point is the purpose of this patch. It fixes a leak of the high 16 bits of the kernel stack address on 32-bit KVM paravirt guests. Fixes CVE-2014-8134. Suggested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/kvm.c9
-rw-r--r--arch/x86/kernel/kvmclock.c1
2 files changed, 8 insertions, 2 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a9c2116..4b6701e 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -419,7 +419,14 @@ static void kvm_leave_lazy_mmu(void)
static void __init paravirt_ops_setup(void)
{
pv_info.name = "KVM";
- pv_info.paravirt_enabled = 1;
+
+ /*
+ * KVM isn't paravirt in the sense of paravirt_enabled. A KVM
+ * guest kernel works like a bare metal kernel with additional
+ * features, and paravirt_enabled is about features that are
+ * missing.
+ */
+ pv_info.paravirt_enabled = 0;
if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
pv_cpu_ops.io_delay = kvm_io_delay;
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 44842d7..e90eca0 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -203,7 +203,6 @@ void __init kvmclock_init(void)
#endif
kvm_get_preset_lpj();
clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
- pv_info.paravirt_enabled = 1;
pv_info.name = "KVM";
if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))