Marc,
On Thu, Mar 16, 2023 at 05:45:45PM +0000, Marc Zyngier wrote:
We walk the userspace PTs to discover what mapping size was used there. However, this can race against the userspace tables being freed, and we end-up in the weeds.
Thankfully, the mm code is being generous and will IPI us when doing so. So let's implement our part of the bargain and disable interrupts around the walk. This ensures that nothing terrible happens during that time.
We still need to handle the removal of the page tables before the walk. For that, allow get_user_mapping_size() to return an error, and make sure this error can be propagated all the way to the the exit handler.
Signed-off-by: Marc Zyngier maz@kernel.org Cc: stable@vger.kernel.org
Looks good. I've squashed in this meaningless diff to make use of an existing helper.
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index e95593736ae3..3b9d4d24c361 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -691,7 +691,7 @@ static int get_user_mapping_size(struct kvm *kvm, u64 addr) return -EFAULT;
/* Oops, the userspace PTs are gone... Replay the fault */ - if (!(pte & PTE_VALID)) + if (!kvm_pte_valid(pte)) return -EAGAIN;
return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level));