From 4bffae22bec7e035e9d5a0c0db7286b6bd258f56 Mon Sep 17 00:00:00 2001 From: Rishabh Bhatnagar Date: Wed, 10 May 2023 18:15:45 +0000 Subject: KVM: x86: revalidate steal time cache if MSR value changes From: Paolo Bonzini commit 901d3765fa804ce42812f1d5b1f3de2dfbb26723 upstream. Commit 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time / preempted status", 2021-11-11) open coded the previous call to kvm_map_gfn, but in doing so it dropped the comparison between the cached guest physical address and the one in the MSR. This cause an incorrect cache hit if the guest modifies the steal time address while the memslots remain the same. This can happen with kexec, in which case the steal time data is written at the address used by the old kernel instead of the old one. While at it, rename the variable from gfn to gpa since it is a plain physical address and not a right-shifted one. Reported-by: Dave Young Reported-by: Xiaoying Yan Analyzed-by: Dr. David Alan Gilbert Cc: David Woodhouse Cc: stable@vger.kernel.org Fixes: 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time / preempted status") Signed-off-by: Paolo Bonzini Signed-off-by: Rishabh Bhatnagar Tested-by: Allen Pais Acked-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 116a225fb26e..0503bb8b64e5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3025,6 +3025,7 @@ static void record_steal_time(struct kvm_vcpu *vcpu) struct gfn_to_hva_cache *ghc = &vcpu->arch.st.cache; struct kvm_steal_time __user *st; struct kvm_memslots *slots; + gpa_t gpa = vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS; u64 steal; u32 version; @@ -3037,13 +3038,12 @@ static void record_steal_time(struct kvm_vcpu *vcpu) slots = kvm_memslots(vcpu->kvm); if (unlikely(slots->generation != ghc->generation || + gpa != ghc->gpa || kvm_is_error_hva(ghc->hva) || !ghc->memslot)) { - gfn_t gfn = vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS; - /* We rely on the fact that it fits in a single page. */ BUILD_BUG_ON((sizeof(*st) - 1) & KVM_STEAL_VALID_BITS); - if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gfn, sizeof(*st)) || + if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gpa, sizeof(*st)) || kvm_is_error_hva(ghc->hva) || !ghc->memslot) return; } -- cgit v1.2.3