Clean up open_exec()/kmalloc() error case handling.

It's a purely theoretical bug, since the kmalloc() failure that
might "leak" file descriptors cannot actually happen (we do not
ever fail small GFP_KERNEL allocations), but it's good to do
things properly.

Noted by Brad Spender.

fs/compat.c

@@ -1387,25 +1387,25 @@ int compat_do_execve(char * filename,
 	int retval;
 	int i;
 
-	file = open_exec(filename);
-
-	retval = PTR_ERR(file);
-	if (IS_ERR(file))
-		return retval;
-
-	sched_exec();
-
 	retval = -ENOMEM;
 	bprm = kmalloc(sizeof(*bprm), GFP_KERNEL);
 	if (!bprm)
 		goto out_ret;
 	memset(bprm, 0, sizeof(*bprm));
 
+	file = open_exec(filename);
+	retval = PTR_ERR(file);
+	if (IS_ERR(file))
+		goto out_kfree;
+
+	sched_exec();
+
 	bprm->p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
 	bprm->file = file;
 	bprm->filename = filename;
 	bprm->interp = filename;
 	bprm->mm = mm_alloc();
+	retval = -ENOMEM;
 	if (!bprm->mm)
 		goto out_file;
 
@@ -1472,6 +1472,8 @@ int compat_do_execve(char * filename,
 		allow_write_access(bprm->file);
 		fput(bprm->file);
 	}
+
+out_kfree:
 	kfree(bprm);
 
 out_ret:

fs/exec.c

@@ -1094,26 +1094,26 @@ int do_execve(char * filename,
 	int retval;
 	int i;
 
-	file = open_exec(filename);
-
-	retval = PTR_ERR(file);
-	if (IS_ERR(file))
-		return retval;
-
-	sched_exec();
-
 	retval = -ENOMEM;
 	bprm = kmalloc(sizeof(*bprm), GFP_KERNEL);
 	if (!bprm)
 		goto out_ret;
 	memset(bprm, 0, sizeof(*bprm));
 
+	file = open_exec(filename);
+	retval = PTR_ERR(file);
+	if (IS_ERR(file))
+		goto out_kfree;
+
+	sched_exec();
+
 	bprm->p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
 
 	bprm->file = file;
 	bprm->filename = filename;
 	bprm->interp = filename;
 	bprm->mm = mm_alloc();
+	retval = -ENOMEM;
 	if (!bprm->mm)
 		goto out_file;
 
@@ -1180,6 +1180,8 @@ int do_execve(char * filename,
 		allow_write_access(bprm->file);
 		fput(bprm->file);
 	}
+
+out_kfree:
 	kfree(bprm);
 
 out_ret: