From: David Matlack dmatlack@google.com
stable inclusion from stable-v5.10.95 commit a447d7f786ec925d1c23f6509255f43ffc2ddffe bugzilla: https://gitee.com/openeuler/kernel/issues/I55EDV
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 7c8a4742c4abe205ec9daf416c9d42fd6b406e8e upstream.
When the TDP MMU is write-protection GFNs for page table protection (as opposed to for dirty logging, or due to the HVA not being writable), it checks if the SPTE is already write-protected and if so skips modifying the SPTE and the TLB flush.
This behavior is incorrect because it fails to check if the SPTE is write-protected for page table protection, i.e. fails to check that MMU-writable is '0'. If the SPTE was write-protected for dirty logging but not page table protection, the SPTE could locklessly be made writable, and vCPUs could still be running with writable mappings cached in their TLB.
Fix this by only skipping setting the SPTE if the SPTE is already write-protected *and* MMU-writable is already clear. Technically, checking only MMU-writable would suffice; a SPTE cannot be writable without MMU-writable being set. But check both to be paranoid and because it arguably yields more readable code.
Fixes: 46044f72c382 ("kvm: x86/mmu: Support write protection for nesting in tdp MMU") Cc: stable@vger.kernel.org Signed-off-by: David Matlack dmatlack@google.com Message-Id: 20220113233020.3986005-2-dmatlack@google.com Reviewed-by: Sean Christopherson seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yu Liao liaoyu15@huawei.com Reviewed-by: Wei Li liwei391@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- arch/x86/kvm/mmu/tdp_mmu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index f2ddf663e72e..7e08efb06839 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1130,12 +1130,12 @@ static bool write_protect_gfn(struct kvm *kvm, struct kvm_mmu_page *root, bool spte_set = false;
tdp_root_for_each_leaf_pte(iter, root, gfn, gfn + 1) { - if (!is_writable_pte(iter.old_spte)) - break; - new_spte = iter.old_spte & ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);
+ if (new_spte == iter.old_spte) + break; + tdp_mmu_set_spte(kvm, &iter, new_spte); spte_set = true; }