From: Vitaly Kuznetsov vkuznets@redhat.com

mainline inclusion from mainline-v5.13-rc2 commit c02027b5742b5aa804ef08a4a9db433295533046 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I990A4 CVE: CVE-2021-47110

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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Currenly, we disable kvmclock from machine_shutdown() hook and this only happens for boot CPU. We need to disable it for all CPUs to guard against memory corruption e.g. on restore from hibernate.

Note, writing '0' to kvmclock MSR doesn't clear memory location, it just prevents hypervisor from updating the location so for the short while after write and while CPU is still alive, the clock remains usable and correct so we don't need to switch to some other clocksource.

Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com Message-Id: 20210414123544.1060604-4-vkuznets@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: liwei liwei728@huawei.com --- arch/x86/include/asm/kvm_para.h | 4 ++-- arch/x86/kernel/kvm.c | 1 + arch/x86/kernel/kvmclock.c | 5 +---- 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 4c723632c036..7caaff8c79ad 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -6,8 +6,6 @@ #include <asm/alternative.h> #include <uapi/asm/kvm_para.h>

-extern void kvmclock_init(void); - #ifdef CONFIG_KVM_GUEST bool kvm_check_and_clear_guest_paused(void); #else @@ -85,6 +83,8 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1, }

#ifdef CONFIG_KVM_GUEST +void kvmclock_init(void); +void kvmclock_disable(void); bool kvm_para_available(void); unsigned int kvm_arch_para_features(void); unsigned int kvm_arch_para_hints(void); diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index d1ccd5bbf623..1c94fdb9207e 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -567,6 +567,7 @@ static void kvm_guest_cpu_offline(void) wrmsrl(MSR_KVM_PV_EOI_EN, 0); kvm_pv_disable_apf(); apf_task_wake_all(); + kvmclock_disable(); }

static int kvm_cpu_online(unsigned int cpu) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 2ec202cb9dfd..d1672a2b1203 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -227,11 +227,9 @@ static void kvm_crash_shutdown(struct pt_regs *regs) } #endif

-static void kvm_shutdown(void) +void kvmclock_disable(void) { native_write_msr(msr_kvm_system_time, 0, 0); - kvm_disable_steal_time(); - native_machine_shutdown(); }

static void __init kvmclock_init_mem(void) @@ -359,7 +357,6 @@ void __init kvmclock_init(void) #endif x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; - machine_ops.shutdown = kvm_shutdown; #ifdef CONFIG_KEXEC_CORE machine_ops.crash_shutdown = kvm_crash_shutdown; #endif