From 8503fea6761de32b72585001ac94e5f81ce8ca44 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 22 Nov 2021 18:20:16 -0500 Subject: [PATCH] KVM: VMX: do not use uninitialized gfn_to_hva_cache An uninitialized gfn_to_hva_cache has ghc->len == 0, which causes the accessors to croak very loudly. While a BUG_ON is definitely _too_ loud and a bug on its own, there is indeed an issue of using the caches in such a way that they could not have been initialized, because ghc->gpa == 0 might match and thus kvm_gfn_to_hva_cache_init would not be called. For the vmcs12_cache, the solution is simply to invoke kvm_gfn_to_hva_cache_init unconditionally: we already know that the cache does not match the current VMCS pointer. For the shadow_vmcs12_cache, there is no similar condition that checks the VMCS link pointer, so invalidate the cache on VMXON. Fixes: cee66664dcd6 ("KVM: nVMX: Use a gfn_to_hva_cache for vmptrld") Acked-by: David Woodhouse Reported-by: syzbot+7b7db8bb4db6fd5e157b@syzkaller.appspotmail.com Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 1e2f66951566..315fa456d368 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4857,6 +4857,7 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu) if (!vmx->nested.cached_vmcs12) goto out_cached_vmcs12; + vmx->nested.shadow_vmcs12_cache.gpa = INVALID_GPA; vmx->nested.cached_shadow_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL_ACCOUNT); if (!vmx->nested.cached_shadow_vmcs12) goto out_cached_shadow_vmcs12; @@ -5289,8 +5290,7 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu) struct gfn_to_hva_cache *ghc = &vmx->nested.vmcs12_cache; struct vmcs_hdr hdr; - if (ghc->gpa != vmptr && - kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, vmptr, VMCS12_SIZE)) { + if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, vmptr, VMCS12_SIZE)) { /* * Reads from an unbacked page return all 1s, * which means that the 32 bits located at the -- 2.11.0