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KVM: arm/arm64: Properly handle faulting of device mappings

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A device mapping is normally always mapped at Stage-2, since there
is very little gain in having it faulted in.

Nonetheless, it is possible to end-up in a situation where the device
mapping has been removed from Stage-2 (userspace munmaped the VFIO
region, and the MMU notifier did its job), but present in a userspace
mapping (userpace has mapped it back at the same address). In such
a situation, the device mapping will be demand-paged as the guest
performs memory accesses.

This requires to be careful when dealing with mapping size, cache
management, and to handle potential execution of a device mapping.

Reported-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191211165651.7889-2-maz@kernel.org
This commit is contained in:
Marc Zyngier 2019-12-11 16:56:48 +00:00
parent 1ce74e96c2
commit 6d674e28f6
1 changed files with 17 additions and 4 deletions
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21
virt/kvm/arm/mmu.c
View File

@ -38,6 +38,11 @@ static unsigned long io_map_base;
#define KVM_S2PTE_FLAG_IS_IOMAP (1UL << 0)
#define KVM_S2_FLAG_LOGGING_ACTIVE (1UL << 1)
static bool is_iomap(unsigned long flags)
{
return flags & KVM_S2PTE_FLAG_IS_IOMAP;
}
static bool memslot_is_logging(struct kvm_memory_slot *memslot)
{
return memslot->dirty_bitmap && !(memslot->flags & KVM_MEM_READONLY);
@ -1698,6 +1703,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
vma_pagesize = vma_kernel_pagesize(vma);
if (logging_active ||
(vma->vm_flags & VM_PFNMAP) ||
!fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
force_pte = true;
vma_pagesize = PAGE_SIZE;
@ -1760,6 +1766,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
writable = false;
}
if (exec_fault && is_iomap(flags))
return -ENOEXEC;
spin_lock(&kvm->mmu_lock);
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
@ -1781,7 +1790,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (writable)
kvm_set_pfn_dirty(pfn);
if (fault_status != FSC_PERM)
if (fault_status != FSC_PERM && !is_iomap(flags))
clean_dcache_guest_page(pfn, vma_pagesize);
if (exec_fault)
@ -1948,9 +1957,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (kvm_is_error_hva(hva) || (write_fault && !writable)) {
if (is_iabt) {
/* Prefetch Abort on I/O address */
kvm_inject_pabt(vcpu, kvm_vcpu_get_hfar(vcpu));
ret = 1;
goto out_unlock;
ret = -ENOEXEC;
goto out;
}
/*
@ -1992,6 +2000,11 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
if (ret == 0)
ret = 1;
out:
if (ret == -ENOEXEC) {
kvm_inject_pabt(vcpu, kvm_vcpu_get_hfar(vcpu));
ret = 1;
}
out_unlock:
srcu_read_unlock(&vcpu->kvm->srcu, idx);
return ret;