The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 9f46c187e2e680ecd9de7983e4d081c3391acc76 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini pbonzini@redhat.com Date: Fri, 20 May 2022 13:48:11 -0400 Subject: [PATCH] KVM: x86/mmu: fix NULL pointer dereference on guest INVPCID
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 kangel@zju.edu.cn Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 56ebc4fb7f91..45e1573f8f1d 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5470,14 +5470,16 @@ 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; } }