4.17-stable review patch. If anyone has any objections, please let me know.
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From: Janosch Frank frankja@linux.ibm.com
commit 1e2c043628c7736dd56536d16c0ce009bc834ae7 upstream.
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: 369cd2121be4 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/userfaultfd.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
--- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -220,24 +220,26 @@ static inline bool userfaultfd_huge_must 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;