thp: verify pmd_trans_huge isn't leaking

pte_trans_huge must not leak in certain vmas like the mmio special pfn or
filebacked mappings.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 840ce9d98f8b..c1a80e00458d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1451,6 +1451,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         pmd = pmd_offset(pud, pg);
                         if (pmd_none(*pmd))
                                 return i ? : -EFAULT;
+                        VM_BUG_ON(pmd_trans_huge(*pmd));
                         pte = pte_offset_map(pmd, pg);
                         if (pte_none(*pte)) {
                                 pte_unmap(pte);
@@ -1675,8 +1676,10 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
         pud_t * pud = pud_alloc(mm, pgd, addr);
         if (pud) {
                 pmd_t * pmd = pmd_alloc(mm, pud, addr);
-                if (pmd)
+                if (pmd) {
+                        VM_BUG_ON(pmd_trans_huge(*pmd));
                         return pte_alloc_map_lock(mm, pmd, addr, ptl);
+                }
         }
         return NULL;
 }
@@ -1895,6 +1898,7 @@ static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
         pmd = pmd_alloc(mm, pud, addr);
         if (!pmd)
                 return -ENOMEM;
+        VM_BUG_ON(pmd_trans_huge(*pmd));
         do {
                 next = pmd_addr_end(addr, end);
                 if (remap_pte_range(mm, pmd, addr, next,
@@ -3471,6 +3475,7 @@ static int __follow_pte(struct mm_struct *mm, unsigned long address,
                 goto out;
 
         pmd = pmd_offset(pud, address);
+        VM_BUG_ON(pmd_trans_huge(*pmd));
         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
                 goto out;