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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: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230316174546.3777507-3-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Marc Zyngier 2023-03-16 17:45:46 +00:00 committed by Oliver Upton
parent e86fc1a3a3
commit 8c2e8ac8ad
1 changed files with 6 additions and 2 deletions
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8
arch/arm64/kvm/mmu.c
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@ -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;