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 --- arch/arm64/kvm/mmu.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index d3d4cdc0f617..e95593736ae3 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -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;