From 58bb69c3ed7c7b606edd07c8cf651510f1d40d71 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 20 May 2022 13:48:11 -0400 Subject: [PATCH] KVM: x86/mmu: fix NULL pointer dereference on guest INVPCID commit 9d92d81746bbd23da80ef78906269bd8bb7ed053 upstream. With shadow paging enabled, the INVPCID instruction results in a call to kvm_mmu_invpcid_gva. If INVPCID is executed with CR0.PG=0, the invlpg callback is not set and the result is a NULL pointer dereference. Fix it trivially by checking for mmu->invlpg before every call. There are other possibilities: - check for CR0.PG, because KVM (like all Intel processors after P5) flushes guest TLB on CR0.PG changes so that INVPCID/INVLPG are a nop with paging disabled - check for EFER.LMA, because KVM syncs and flushes when switching MMU contexts outside of 64-bit mode All of these are tricky, go for the simple solution. This is CVE-2022-1789. Reported-by: Yongkang Jia Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini [fix conflict due to missing 9b8852a7ef3229db20d44b5420c854e4a4434a14] Signed-off-by: Vegard Nossum Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/mmu/mmu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index c5fd00945e752..3417405077adf 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5396,14 +5396,16 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid) uint i; if (pcid == kvm_get_active_pcid(vcpu)) { - mmu->invlpg(vcpu, gva, mmu->root_hpa); + if (mmu->invlpg) + mmu->invlpg(vcpu, gva, mmu->root_hpa); tlb_flush = true; } for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { if (VALID_PAGE(mmu->prev_roots[i].hpa) && pcid == kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd)) { - mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa); + if (mmu->invlpg) + mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa); tlb_flush = true; } } -- 2.39.5