mm: don't call pte_unmap() against an improper pte

There are some places where we do like:

	pte = pte_map();
	do {
		(do break in some conditions)
	} while (pte++, ...);
	pte_unmap(pte - 1);

But if the loop breaks at the first loop, pte_unmap() unmaps invalid pte.

This patch is a fix for this problem.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewd-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 7e91b5f9f690..60ea601e03ea 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -641,6 +641,7 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
                 unsigned long addr, unsigned long end)
 {
+        pte_t *orig_src_pte, *orig_dst_pte;
         pte_t *src_pte, *dst_pte;
         spinlock_t *src_ptl, *dst_ptl;
         int progress = 0;
@@ -654,6 +655,8 @@ again:
         src_pte = pte_offset_map_nested(src_pmd, addr);
         src_ptl = pte_lockptr(src_mm, src_pmd);
         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+        orig_src_pte = src_pte;
+        orig_dst_pte = dst_pte;
         arch_enter_lazy_mmu_mode();
 
         do {
@@ -677,9 +680,9 @@ again:
 
         arch_leave_lazy_mmu_mode();
         spin_unlock(src_ptl);
-        pte_unmap_nested(src_pte - 1);
+        pte_unmap_nested(orig_src_pte);
         add_mm_rss(dst_mm, rss[0], rss[1]);
-        pte_unmap_unlock(dst_pte - 1, dst_ptl);
+        pte_unmap_unlock(orig_dst_pte, dst_ptl);
         cond_resched();
         if (addr != end)
                 goto again;
@@ -1820,10 +1823,10 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
         token = pmd_pgtable(*pmd);
 
         do {
-                err = fn(pte, token, addr, data);
+                err = fn(pte++, token, addr, data);
                 if (err)
                         break;
-        } while (pte++, addr += PAGE_SIZE, addr != end);
+        } while (addr += PAGE_SIZE, addr != end);
 
         arch_leave_lazy_mmu_mode();