Messages in this thread | | | Date | Wed, 27 Jan 2021 16:09:21 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte |
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On Wed, 27 Jan 2021 04:33:49 -0500 Miaohe Lin <linmiaohe@huawei.com> wrote:
> For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP, > pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set > to the relevant page table entry. So in page_vma_mapped_walk_done(), we may > do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking > pvmw->page against PageHuge before trying to do pte_unmap(). >
What are the runtime consequences of this? Is there a workload which is known to trigger it?
IOW, how do we justify a -stable backport of this fix?
> > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -213,7 +213,8 @@ struct page_vma_mapped_walk { > > static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) > { > - if (pvmw->pte) > + /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */ > + if (pvmw->pte && !PageHuge(pvmw->page)) > pte_unmap(pvmw->pte); > if (pvmw->ptl) > spin_unlock(pvmw->ptl); > -- > 2.19.1
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