Messages in this thread | | | Date | Wed, 13 Sep 2017 15:18:30 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] mm, oom_reaper: skip mm structs with mmu notifiers |
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On Wed, Sep 13, 2017 at 01:34:27PM +0200, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Andrea has noticed that the oom_reaper doesn't invalidate the range > via mmu notifiers (mmu_notifier_invalidate_range_start, > mmu_notifier_invalidate_range_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. > > Changes since v1 > - move mm_has_notifiers check after we hold mmap_sem to prevent from > any potential races as per Andrea > > Fixes: aac453635549 ("mm, oom: introduce oom reaper") > Noticed-by: Andrea Arcangeli <aarcange@redhat.com> > Cc: stable > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > Hi, > I have posted this as an RFC previously [1]. I have updated > the changelog to be more clear about the issue and moved the > mm_has_notifiers after the lock has been take based on Andrea's > suggestion. > > Can we merge this? > > [1] http://lkml.kernel.org/r/20170830084600.17491-1-mhocko@kernel.org > > include/linux/mmu_notifier.h | 5 +++++ > mm/oom_kill.c | 16 ++++++++++++++++ > 2 files changed, 21 insertions(+)
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
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