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userfaultfd: hugetlbfs: fix userfaultfd_huge_must_wait() pte access 

Use huge_ptep_get() to translate huge ptes to normal ptes so we can
check them with the huge_pte_* functions.  Otherwise some architectures
will check the wrong values and will not wait for userspace to bring in
the memory.

Link: http://lkml.kernel.org/r/20180626132421.78084-1-frankja@linux.ibm.com
Fixes: 369cd2121b ("userfaultfd: hugetlbfs: userfaultfd_huge_must_wait for hugepmd ranges")
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Janosch Frank 2018-07-03 17:02:39 -07:00 committed by Linus Torvalds
parent 410da1e12f
commit 1e2c043628
1 changed files with 7 additions and 5 deletions
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12
fs/userfaultfd.c
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@ -222,24 +222,26 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
unsigned long reason)
{
struct mm_struct *mm = ctx->mm;
pte_t *pte;
pte_t *ptep, pte;
bool ret = true;
VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
pte = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
if (!pte)
ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
if (!ptep)
goto out;
ret = false;
pte = huge_ptep_get(ptep);
/*
* Lockless access: we're in a wait_event so it's ok if it
* changes under us.
*/
if (huge_pte_none(*pte))
if (huge_pte_none(pte))
ret = true;
if (!huge_pte_write(*pte) && (reason & VM_UFFD_WP))
if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
ret = true;
out:
return ret;