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     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/linux/stuff/linux-CVE-2016-5195.u	Fri Sep 08 15:02:42 2017 +0200
     1.3 @@ -0,0 +1,87 @@
     1.4 +https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5195
     1.5 +--- a/include/linux/mm.h
     1.6 ++++ b/include/linux/mm.h
     1.7 +@@ -1611,6 +1611,7 @@ struct page *follow_page(struct vm_area_struct *, unsigned long address,
     1.8 + #define FOLL_MLOCK	0x40	/* mark page as mlocked */
     1.9 + #define FOLL_SPLIT	0x80	/* don't return transhuge pages, split them */
    1.10 + #define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */
    1.11 ++#define FOLL_COW	0x4000	/* internal GUP flag */
    1.12 + 
    1.13 + typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
    1.14 + 			void *data);
    1.15 +diff --git a/mm/memory.c b/mm/memory.c
    1.16 +index 675b211296fd..2917e9b2e4d4 100644
    1.17 +--- a/mm/memory.c
    1.18 ++++ b/mm/memory.c
    1.19 +@@ -1427,6 +1427,24 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
    1.20 + }
    1.21 + EXPORT_SYMBOL_GPL(zap_vma_ptes);
    1.22 + 
    1.23 ++static inline bool can_follow_write_pte(pte_t pte, struct page *page,
    1.24 ++					unsigned int flags)
    1.25 ++{
    1.26 ++	if (pte_write(pte))
    1.27 ++		return true;
    1.28 ++
    1.29 ++	/*
    1.30 ++	 * Make sure that we are really following CoWed page. We do not really
    1.31 ++	 * have to care about exclusiveness of the page because we only want
    1.32 ++	 * to ensure that once COWed page hasn't disappeared in the meantime
    1.33 ++	 * or it hasn't been merged to a KSM page.
    1.34 ++	 */
    1.35 ++	if ((flags & FOLL_FORCE) && (flags & FOLL_COW))
    1.36 ++		return page && PageAnon(page) && !PageKsm(page);
    1.37 ++
    1.38 ++	return false;
    1.39 ++}
    1.40 ++
    1.41 + /**
    1.42 +  * follow_page - look up a page descriptor from a user-virtual address
    1.43 +  * @vma: vm_area_struct mapping @address
    1.44 +@@ -1509,10 +1527,13 @@ split_fallthrough:
    1.45 + 	pte = *ptep;
    1.46 + 	if (!pte_present(pte))
    1.47 + 		goto no_page;
    1.48 +-	if ((flags & FOLL_WRITE) && !pte_write(pte))
    1.49 +-		goto unlock;
    1.50 + 
    1.51 + 	page = vm_normal_page(vma, address, pte);
    1.52 ++	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, page, flags)) {
    1.53 ++		pte_unmap_unlock(ptep, ptl);
    1.54 ++		return NULL;
    1.55 ++	}
    1.56 ++
    1.57 + 	if (unlikely(!page)) {
    1.58 + 		if ((flags & FOLL_DUMP) ||
    1.59 + 		    !is_zero_pfn(pte_pfn(pte)))
    1.60 +@@ -1555,7 +1576,7 @@ split_fallthrough:
    1.61 + 			unlock_page(page);
    1.62 + 		}
    1.63 + 	}
    1.64 +-unlock:
    1.65 ++
    1.66 + 	pte_unmap_unlock(ptep, ptl);
    1.67 + out:
    1.68 + 	return page;
    1.69 +@@ -1789,17 +1810,13 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
    1.70 + 				 * The VM_FAULT_WRITE bit tells us that
    1.71 + 				 * do_wp_page has broken COW when necessary,
    1.72 + 				 * even if maybe_mkwrite decided not to set
    1.73 +-				 * pte_write. We can thus safely do subsequent
    1.74 +-				 * page lookups as if they were reads. But only
    1.75 +-				 * do so when looping for pte_write is futile:
    1.76 +-				 * in some cases userspace may also be wanting
    1.77 +-				 * to write to the gotten user page, which a
    1.78 +-				 * read fault here might prevent (a readonly
    1.79 +-				 * page might get reCOWed by userspace write).
    1.80 ++				 * pte_write. We cannot simply drop FOLL_WRITE
    1.81 ++				 * here because the COWed page might be gone by
    1.82 ++				 * the time we do the subsequent page lookups.
    1.83 + 				 */
    1.84 + 				if ((ret & VM_FAULT_WRITE) &&
    1.85 + 				    !(vma->vm_flags & VM_WRITE))
    1.86 +-					foll_flags &= ~FOLL_WRITE;
    1.87 ++					foll_flags |= FOLL_COW;
    1.88 + 
    1.89 + 				cond_resched();
    1.90 + 			}