Commit 8c2e8ac8 authored by Marc Zyngier's avatar Marc Zyngier Committed by Oliver Upton
Browse files

KVM: arm64: Check for kvm_vma_mte_allowed in the critical section 



On page fault, we find about the VMA that backs the page fault
early on, and quickly release the mmap_read_lock. However, using
the VMA pointer after the critical section is pretty dangerous,
as a teardown may happen in the meantime and the VMA be long gone.

Move the sampling of the MTE permission early, and NULL-ify the
VMA pointer after that, just to be on the safe side.

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230316174546.3777507-3-maz@kernel.org


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent e86fc1a3

arch/arm64/kvm/mmu.c

+6 −2
Original line number Diff line number Diff line
@@ -1218,7 +1218,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 
{

	int ret = 0;

	bool write_fault, writable, force_pte = false;

	bool exec_fault;

	bool exec_fault, mte_allowed;

	bool device = false;

	unsigned long mmu_seq;

	struct kvm *kvm = vcpu->kvm;
@@ -1309,6 +1309,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 
		fault_ipa &= ~(vma_pagesize - 1);



	gfn = fault_ipa >> PAGE_SHIFT;

	mte_allowed = kvm_vma_mte_allowed(vma);



	/* Don't use the VMA after the unlock -- it may have vanished */

	vma = NULL;



	/*

	 * Read mmu_invalidate_seq so that KVM can detect if the results of
@@ -1379,7 +1383,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 


	if (fault_status != ESR_ELx_FSC_PERM && !device && kvm_has_mte(kvm)) {

		/* Check the VMM hasn't introduced a new disallowed VMA */

		if (kvm_vma_mte_allowed(vma)) {

		if (mte_allowed) {

			sanitise_mte_tags(kvm, pfn, vma_pagesize);

		} else {

			ret = -EFAULT;