From 17763049e8d8dc0d8b44fa007efe27bcc9ca2d1e Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 25 May 2021 15:31:55 +0000 Subject: [PATCH] KVM: VMX: Disable preemption when probing user return MSRs stable inclusion from stable-5.10.38 commit 31f29749ee970c251b3a7e5b914108425940d089 bugzilla: 51875 CVE: NA -------------------------------- commit 5104d7ffcf24749939bea7fdb5378d186473f890 upstream. Disable preemption when probing a user return MSR via RDSMR/WRMSR. If the MSR holds a different value per logical CPU, the WRMSR could corrupt the host's value if KVM is preempted between the RDMSR and WRMSR, and then rescheduled on a different CPU. Opportunistically land the helper in common x86, SVM will use the helper in a future commit. Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation") Cc: stable@vger.kernel.org Cc: Xiaoyao Li Signed-off-by: Sean Christopherson Message-Id: <20210504171734.1434054-6-seanjc@google.com> Reviewed-by: Jim Mattson Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Acked-by: Weilong Chen Signed-off-by: Zheng Zengkai --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx/vmx.c | 5 +---- arch/x86/kvm/x86.c | 16 ++++++++++++++++ 3 files changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 5959566e4af7..90c34de3fefc 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1682,6 +1682,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low, unsigned long icr, int op_64_bit); void kvm_define_user_return_msr(unsigned index, u32 msr); +int kvm_probe_user_return_msr(u32 msr); int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask); u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 532410841488..c50f5b48da67 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6877,12 +6877,9 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu) for (i = 0; i < ARRAY_SIZE(vmx_uret_msrs_list); ++i) { u32 index = vmx_uret_msrs_list[i]; - u32 data_low, data_high; int j = vmx->nr_uret_msrs; - if (rdmsr_safe(index, &data_low, &data_high) < 0) - continue; - if (wrmsr_safe(index, data_low, data_high) < 0) + if (kvm_probe_user_return_msr(index)) continue; vmx->guest_uret_msrs[j].slot = i; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 66889100405a..e90a31b5215d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -365,6 +365,22 @@ static void kvm_on_user_return(struct user_return_notifier *urn) } } +int kvm_probe_user_return_msr(u32 msr) +{ + u64 val; + int ret; + + preempt_disable(); + ret = rdmsrl_safe(msr, &val); + if (ret) + goto out; + ret = wrmsrl_safe(msr, val); +out: + preempt_enable(); + return ret; +} +EXPORT_SYMBOL_GPL(kvm_probe_user_return_msr); + void kvm_define_user_return_msr(unsigned slot, u32 msr) { BUG_ON(slot >= KVM_MAX_NR_USER_RETURN_MSRS); -- GitLab