1 files changed, 25 insertions, 35 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 89fe414645e9..c674aa8d3c31 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -521,7 +521,7 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
  * Allocate a new mm structure and copy contents from the
  * mm structure of the passed in task structure.
  */
-static struct mm_struct *dup_mm(struct task_struct *tsk)
+struct mm_struct *dup_mm(struct task_struct *tsk)
 {
         struct mm_struct *mm, *oldmm = current->mm;
         int err;
@@ -805,12 +805,6 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
                 goto out;
         }
 
-        /*
-         * Note: we may be using current for both targets (See exec.c)
-         * This works because we cache current->files (old) as oldf. Don't
-         * break this.
-         */
-        tsk->files = NULL;
         newf = dup_fd(oldf, &error);
         if (!newf)
                 goto out;
@@ -846,34 +840,6 @@ static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
         return 0;
 }
 
-/*
- *      Helper to unshare the files of the current task.
- *      We don't want to expose copy_files internals to
- *      the exec layer of the kernel.
- */
-
-int unshare_files(void)
-{
-        struct files_struct *files  = current->files;
-        int rc;
-
-        BUG_ON(!files);
-
-        /* This can race but the race causes us to copy when we don't
-           need to and drop the copy */
-        if(atomic_read(&files->count) == 1)
-        {
-                atomic_inc(&files->count);
-                return 0;
-        }
-        rc = copy_files(0, current);
-        if(rc)
-                current->files = files;
-        return rc;
-}
-
-EXPORT_SYMBOL(unshare_files);
-
 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct sighand_struct *sig;
@@ -1811,3 +1777,27 @@ bad_unshare_cleanup_thread:
 bad_unshare_out:
         return err;
 }
+
+/*
+ *      Helper to unshare the files of the current task.
+ *      We don't want to expose copy_files internals to
+ *      the exec layer of the kernel.
+ */
+
+int unshare_files(struct files_struct **displaced)
+{
+        struct task_struct *task = current;
+        struct files_struct *copy = NULL;
+        int error;
+
+        error = unshare_fd(CLONE_FILES, &copy);
+        if (error || !copy) {
+                *displaced = NULL;
+                return error;
+        }
+        *displaced = task->files;
+        task_lock(task);
+        task->files = copy;
+        task_unlock(task);
+        return 0;
+}