On Thu, Sep 09, 2021 at 06:22:39PM +0200, David Hildenbrand wrote: > Resend because I missed ccing people on the actual patches ... > > RFC because the patches are essentially untested and I did not actually > try to trigger any of the things these patches are supposed to fix. It > merely matches my current understanding (and what other code does :) ). I > did compile-test as far as possible. > > After learning more about the wonderful world of page tables and their > interaction with the mmap_sem and VMAs, I spotted some issues in our > page table walkers that allow user space to trigger nasty behavior when > playing dirty tricks with munmap() or mmap() of hugetlb. While some issues > should be hard to trigger, others are fairly easy because we provide > conventient interfaces (e.g., KVM_S390_GET_SKEYS and KVM_S390_SET_SKEYS). > > Future work: > - Don't use get_locked_pte() when it's not required to actually allocate > page tables -- similar to how storage keys are now handled. Examples are > get_pgste() and __gmap_zap. > - Don't use get_locked_pte() and instead let page fault logic allocate page > tables when we actually do need page tables -- also, similar to how > storage keys are now handled. Examples are set_pgste_bits() and > pgste_perform_essa(). > - Maybe switch to mm/pagewalk.c to avoid custom page table walkers. For > __gmap_zap() that's very easy. > > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> > Cc: Janosch Frank <frankja@xxxxxxxxxxxxx> > Cc: Cornelia Huck <cohuck@xxxxxxxxxx> > Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> > Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> > Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> > Cc: Niklas Schnelle <schnelle@xxxxxxxxxxxxx> > Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx> > Cc: Ulrich Weigand <Ulrich.Weigand@xxxxxxxxxx> For the whole series: Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Christian, given that this is mostly about KVM I'd assume this should go via the KVM tree. Patch 6 (pci_mmio) is already upstream.
