[PATCH] mbind: fix verify_pages pte_page

Strict mbind's check that pages already mapped are on right node has been
using pte_page without checking if pfn_valid, and without page_table_lock
to prevent spurious failures when try_to_unmap_one intervenes between the
pte_present and the pte_page.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 14 insertions, 5 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 39252c732db2..c512cc911e22 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -242,6 +242,9 @@ static int
 verify_pages(struct mm_struct *mm,
              unsigned long addr, unsigned long end, unsigned long *nodes)
 {
+        int err = 0;
+
+        spin_lock(&mm->page_table_lock);
         while (addr < end) {
                 struct page *p;
                 pte_t *pte;
@@ -268,17 +271,23 @@ verify_pages(struct mm_struct *mm,
                 }
                 p = NULL;
                 pte = pte_offset_map(pmd, addr);
-                if (pte_present(*pte))
-                        p = pte_page(*pte);
+                if (pte_present(*pte)) {
+                        unsigned long pfn = pte_pfn(*pte);
+                        if (pfn_valid(pfn))
+                                p = pfn_to_page(pfn);
+                }
                 pte_unmap(pte);
                 if (p) {
                         unsigned nid = page_to_nid(p);
-                        if (!test_bit(nid, nodes))
-                                return -EIO;
+                        if (!test_bit(nid, nodes)) {
+                                err = -EIO;
+                                break;
+                        }
                 }
                 addr += PAGE_SIZE;
         }
-        return 0;
+        spin_unlock(&mm->page_table_lock);
+        return err;
 }
 
 /* Step 1: check the range */