Messages in this thread | | | Subject | Re: [PATCH resend RFC 0/9] s390: fixes, cleanups and optimizations for page table walkers | From | Christian Borntraeger <> | Date | Tue, 28 Sep 2021 18:03:46 +0200 |
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Am 09.09.21 um 18:22 schrieb David Hildenbrand: > 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@de.ibm.com> > Cc: Janosch Frank <frankja@linux.ibm.com> > Cc: Cornelia Huck <cohuck@redhat.com> > Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> > Cc: Heiko Carstens <hca@linux.ibm.com> > Cc: Vasily Gorbik <gor@linux.ibm.com> > Cc: Niklas Schnelle <schnelle@linux.ibm.com> > Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> > Cc: Ulrich Weigand <Ulrich.Weigand@de.ibm.com> > > David Hildenbrand (9): > s390/gmap: validate VMA in __gmap_zap() > s390/gmap: don't unconditionally call pte_unmap_unlock() in > __gmap_zap() > s390/mm: validate VMA in PGSTE manipulation functions > s390/mm: fix VMA and page table handling code in storage key handling > functions > s390/uv: fully validate the VMA before calling follow_page() > s390/pci_mmio: fully validate the VMA before calling follow_pte() > s390/mm: no need for pte_alloc_map_lock() if we know the pmd is > present > s390/mm: optimize set_guest_storage_key() > s390/mm: optimize reset_guest_reference_bit() > > arch/s390/kernel/uv.c | 2 +- > arch/s390/mm/gmap.c | 11 +++- > arch/s390/mm/pgtable.c | 109 +++++++++++++++++++++++++++------------ > arch/s390/pci/pci_mmio.c | 4 +- > 4 files changed, 89 insertions(+), 37 deletions(-) >
Thanks applied. Will run some test on those commits, but its already pushed out to my next tree to give it some coverage. g
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