From 6c01aba05b12c1f078197a45a711bcc5092b2a1c Mon Sep 17 00:00:00 2001
From: Scott Shawcroft <scott@tannewt.org>
Date: Wed, 13 Mar 2019 15:17:07 -0700
Subject: [PATCH] Prevent other filesystem changes besides file writes

Such as moving files, adding directories and changing the label.
---
 extmod/vfs_fat.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/extmod/vfs_fat.c b/extmod/vfs_fat.c
index c7e8a81e81..20d3e3e5ce 100644
--- a/extmod/vfs_fat.c
+++ b/extmod/vfs_fat.c
@@ -39,7 +39,7 @@
 #include "lib/oofatfs/ff.h"
 #include "extmod/vfs_fat.h"
 #include "lib/timeutils/timeutils.h"
-
+#include "supervisor/filesystem.h"
 #include "supervisor/shared/translate.h"
 
 #if _MAX_SS == _MIN_SS
@@ -99,6 +99,12 @@ STATIC mp_obj_t fat_vfs_make_new(const mp_obj_type_t *type, size_t n_args, const
     return MP_OBJ_FROM_PTR(vfs);
 }
 
+STATIC void verify_fs_writable(fs_user_mount_t *vfs) {
+    if (!filesystem_is_writable_by_python(vfs)) {
+        mp_raise_OSError(MP_EROFS);
+    }
+}
+
 #if _FS_REENTRANT
 STATIC mp_obj_t fat_vfs_del(mp_obj_t self_in) {
     mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(self_in);
@@ -201,6 +207,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(fat_vfs_ilistdir_obj, 1, 2, fat_vfs_i
 
 STATIC mp_obj_t fat_vfs_remove_internal(mp_obj_t vfs_in, mp_obj_t path_in, mp_int_t attr) {
     mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
+    verify_fs_writable(self);
     const char *path = mp_obj_str_get_str(path_in);
 
     FILINFO fno;
@@ -235,6 +242,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_rmdir_obj, fat_vfs_rmdir);
 
 STATIC mp_obj_t fat_vfs_rename(mp_obj_t vfs_in, mp_obj_t path_in, mp_obj_t path_out) {
     mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
+    verify_fs_writable(self);
     const char *old_path = mp_obj_str_get_str(path_in);
     const char *new_path = mp_obj_str_get_str(path_out);
 
@@ -271,6 +279,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(fat_vfs_rename_obj, fat_vfs_rename);
 
 STATIC mp_obj_t fat_vfs_mkdir(mp_obj_t vfs_in, mp_obj_t path_o) {
     mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
+    verify_fs_writable(self);
     const char *path = mp_obj_str_get_str(path_o);
     FRESULT res = f_mkdir(&self->fatfs, path);
     if (res == FR_OK) {
@@ -435,6 +444,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(fat_vfs_getlabel_obj, vfs_fat_getlabel);
 
 STATIC mp_obj_t vfs_fat_setlabel(mp_obj_t self_in, mp_obj_t label_in) {
     fs_user_mount_t *self = MP_OBJ_TO_PTR(self_in);
+    verify_fs_writable(self);
     const char *label_str = mp_obj_str_get_str(label_in);
     FRESULT res = f_setlabel(&self->fatfs, label_str);
     if (res != FR_OK) {