• Michal Hocko's avatar
    mm, oom_reaper: skip mm structs with mmu notifiers · 4d4bbd85
    Michal Hocko authored
    Andrea has noticed that the oom_reaper doesn't invalidate the range via
    mmu notifiers (mmu_notifier_invalidate_range_start/end) and that can
    corrupt the memory of the kvm guest for example.
    
    tlb_flush_mmu_tlbonly already invokes mmu notifiers but that is not
    sufficient as per Andrea:
    
     "mmu_notifier_invalidate_range cannot be used in replacement of
      mmu_notifier_invalidate_range_start/end. For KVM
      mmu_notifier_invalidate_range is a noop and rightfully so. A MMU
      notifier implementation has to implement either ->invalidate_range
      method or the invalidate_range_start/end methods, not both. And if you
      implement invalidate_range_start/end like KVM is forced to do, calling
      mmu_notifier_invalidate_range in common code is a noop for KVM.
    
      For those MMU notifiers that can get away only implementing
      ->invalidate_range, the ->invalidate_range is implicitly called by
      mmu_notifier_invalidate_range_end(). And only those secondary MMUs
      that share the same pagetable with the primary MMU (like AMD iommuv2)
      can get away only implementing ->invalidate_range"
    
    As the callback is allowed to sleep and the implementation is out of
    hand of the MM it is safer to simply bail out if there is an mmu
    notifier registered.  In order to not fail too early make the
    mm_has_notifiers check under the oom_lock and have a little nap before
    failing to give the current oom victim some more time to exit.
    
    [akpm@linux-foundation.org: coding-style fixes]
    Link: http://lkml.kernel.org/r/20170913113427.2291-1-mhocko@kernel.org
    Fixes: aac45363 ("mm, oom: introduce oom reaper")
    Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Reported-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
    Reviewed-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    4d4bbd85
oom_kill.c 29.3 KB