do_mbind(): fix memory leak

If migrate_prep is failed, new variable is leaked.  This patch fixes it.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

@@ -1024,7 +1024,7 @@ static long do_mbind(unsigned long start, unsigned long len,
 
 		err = migrate_prep();
 		if (err)
-			return err;
+			goto mpol_out;
 	}
 	{
 		NODEMASK_SCRATCH(scratch);
@@ -1039,10 +1039,9 @@ static long do_mbind(unsigned long start, unsigned long len,
 			err = -ENOMEM;
 		NODEMASK_SCRATCH_FREE(scratch);
 	}
-	if (err) {
-		mpol_put(new);
-		return err;
-	}
+	if (err)
+		goto mpol_out;
+
 	vma = check_range(mm, start, end, nmask,
 			  flags | MPOL_MF_INVERT, &pagelist);
 
@@ -1062,6 +1061,7 @@ static long do_mbind(unsigned long start, unsigned long len,
 		putback_lru_pages(&pagelist);
 
 	up_write(&mm->mmap_sem);
+ mpol_out:
 	mpol_put(new);
 	return err;
 }