2.6.31.9-rc1

 kernel

diff --git a/kernel/futex.c b/kernel/futex.c
index c0a020f..ba7f0be 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -303,8 +303,14 @@ void put_futex_key(int fshared, union futex_key *key)
  */
 static int fault_in_user_writeable(u32 __user *uaddr)
 {
-   int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
-             1, 1, 0, NULL, NULL);
+   struct mm_struct *mm = current->mm;
+   int ret;
+
+   down_read(&mm->mmap_sem);
+   ret = get_user_pages(current, mm, (unsigned long)uaddr,
+              1, 1, 0, NULL, NULL);
+   up_read(&mm->mmap_sem);
+
    return ret < 0 ? ret : 0;
 }