Commit ba0a194f authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Allocate the lm_root before allocating PAE roots 



Allocate lm_root before the PAE roots so that the PAE roots aren't
leaked if the memory allocation for the lm_root happens to fail.

Note, KVM can still leak PAE roots if mmu_check_root() fails on a guest's
PDPTR, or if mmu_alloc_root() fails due to MMU pages not being available.
Those issues will be fixed in future commits.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-5-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b37233c9

arch/x86/kvm/mmu/mmu.c

+31 −33
Original line number Diff line number Diff line
@@ -3314,21 +3314,38 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) 
	 * the shadow page table may be a PAE or a long mode page table.

	 */

	pm_mask = PT_PRESENT_MASK;

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)

		pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;



	/*

		 * Allocate the page for the PDPTEs when shadowing 32-bit NPT

		 * with 64-bit only when needed.  Unlike 32-bit NPT, it doesn't

		 * need to be in low mem.  See also lm_root below.

	 * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP

	 * tables are allocated and initialized at root creation as there is no

	 * equivalent level in the guest's NPT to shadow.  Allocate the tables

	 * on demand, as running a 32-bit L1 VMM is very rare.  Unlike 32-bit

	 * NPT, the PDP table doesn't need to be in low mem.  Preallocate the

	 * pages so that the PAE roots aren't leaked on failure.

	 */

		if (!mmu->pae_root) {

			WARN_ON_ONCE(!tdp_enabled);

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL &&

	    (!mmu->pae_root || !mmu->lm_root)) {

		u64 *lm_root, *pae_root;



		if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->lm_root))

			return -EIO;



		pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

		if (!pae_root)

			return -ENOMEM;



			mmu->pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

			if (!mmu->pae_root)

		lm_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

		if (!lm_root) {

			free_page((unsigned long)pae_root);

			return -ENOMEM;

		}



		mmu->pae_root = pae_root;

		mmu->lm_root = lm_root;



		lm_root[0] = __pa(mmu->pae_root) | pm_mask;

	}



	for (i = 0; i < 4; ++i) {
@@ -3350,30 +3367,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) 
			return -ENOSPC;

		mmu->pae_root[i] = root | pm_mask;

	}

	mmu->root_hpa = __pa(mmu->pae_root);



	/*

	 * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP

	 * tables are allocated and initialized at MMU creation as there is no

	 * equivalent level in the guest's NPT to shadow.  Allocate the tables

	 * on demand, as running a 32-bit L1 VMM is very rare.  The PDP is

	 * handled above (to share logic with PAE), deal with the PML4 here.

	 */

	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {

		if (mmu->lm_root == NULL) {

			u64 *lm_root;



			lm_root = (void*)get_zeroed_page(GFP_KERNEL_ACCOUNT);

			if (!lm_root)

				return -ENOMEM;



			lm_root[0] = __pa(mmu->pae_root) | pm_mask;



			mmu->lm_root = lm_root;

		}



	if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)

		mmu->root_hpa = __pa(mmu->lm_root);

	}

	else

		mmu->root_hpa = __pa(mmu->pae_root);



set_root_pgd:

	mmu->root_pgd = root_pgd;