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authorAndy Lutomirski <luto@amacapital.net>2014-12-05 19:03:28 -0800
committerPaolo Bonzini <pbonzini@redhat.com>2014-12-10 12:49:39 +0100
commit29fa6825463c97e5157284db80107d1bfac5d77b (patch)
treebb0d1cb44bea9cfed3c3d57185219e1249558b1c
parente08e833616f7eefebdacfd1d743d80ff3c3b2585 (diff)
downloadlinux-29fa6825463c97e5157284db80107d1bfac5d77b.tar.bz2
x86, kvm: Clear paravirt_enabled on KVM guests for espfix32's benefit
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. Cc: stable@vger.kernel.org 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>
-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 f6945bef2cd1..94f643484300 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -283,7 +283,14 @@ NOKPROBE_SYMBOL(do_async_page_fault);
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 0bf3467d7f30..42caaef897c8 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -261,7 +261,6 @@ 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))