extmod/vfs: Add finaliser to ilistdir to close directory handle.

When iterating over filesystem/folders with os.iterdir(), an open file
(directory) handle is used internally.  Currently this file handle is only
closed once the iterator is completely drained, eg. once all entries have
been looped over / converted into list etc.

If a program opens an iterdir but does not loop over it, or starts to loop
over the iterator but breaks out of the loop, then the handle never gets
closed.  In this state, when the iter object is cleaned up by the garbage
collector this open handle can cause corruption of the filesystem.

Fixes issues #6568 and #8506.

1 files changed, 23 insertions, 2 deletions

diff --git a/extmod/vfs_lfsx.c b/extmod/vfs_lfsx.c
index dbd32338c..fbfeaa5cc 100644
--- a/extmod/vfs_lfsx.c
+++ b/extmod/vfs_lfsx.c
@@ -36,6 +36,10 @@
 #include "extmod/vfs.h"
 #include "shared/timeutils/timeutils.h"
 
+#if !MICROPY_ENABLE_FINALISER
+#error "MICROPY_VFS_LFS requires MICROPY_ENABLE_FINALISER"
+#endif
+
 STATIC int MP_VFS_LFSx(dev_ioctl)(const struct LFSx_API (config) * c, int cmd, int arg, bool must_return_int) {
     mp_obj_t ret = mp_vfs_blockdev_ioctl(c->context, cmd, arg);
     int ret_i = 0;
@@ -155,6 +159,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(MP_VFS_LFSx(open_obj), MP_VFS_LFSx(file_open));
 typedef struct MP_VFS_LFSx (_ilistdir_it_t) {
     mp_obj_base_t base;
     mp_fun_1_t iternext;
+    mp_fun_1_t finaliser;
     bool is_str;
     MP_OBJ_VFS_LFSx *vfs;
     LFSx_API(dir_t) dir;
@@ -163,11 +168,16 @@ typedef struct MP_VFS_LFSx (_ilistdir_it_t) {
 STATIC mp_obj_t MP_VFS_LFSx(ilistdir_it_iternext)(mp_obj_t self_in) {
     MP_VFS_LFSx(ilistdir_it_t) * self = MP_OBJ_TO_PTR(self_in);
 
+    if (self->vfs == NULL) {
+        return MP_OBJ_STOP_ITERATION;
+    }
+
     struct LFSx_API (info) info;
     for (;;) {
         int ret = LFSx_API(dir_read)(&self->vfs->lfs, &self->dir, &info);
         if (ret == 0) {
             LFSx_API(dir_close)(&self->vfs->lfs, &self->dir);
+            self->vfs = NULL;
             return MP_OBJ_STOP_ITERATION;
         }
         if (!(info.name[0] == '.' && (info.name[1] == '\0'
@@ -190,6 +200,14 @@ STATIC mp_obj_t MP_VFS_LFSx(ilistdir_it_iternext)(mp_obj_t self_in) {
     return MP_OBJ_FROM_PTR(t);
 }
 
+STATIC mp_obj_t MP_VFS_LFSx(ilistdir_it_del)(mp_obj_t self_in) {
+    MP_VFS_LFSx(ilistdir_it_t) * self = MP_OBJ_TO_PTR(self_in);
+    if (self->vfs != NULL) {
+        LFSx_API(dir_close)(&self->vfs->lfs, &self->dir);
+    }
+    return mp_const_none;
+}
+
 STATIC mp_obj_t MP_VFS_LFSx(ilistdir_func)(size_t n_args, const mp_obj_t *args) {
     MP_OBJ_VFS_LFSx *self = MP_OBJ_TO_PTR(args[0]);
     bool is_str_type = true;
@@ -203,14 +221,17 @@ STATIC mp_obj_t MP_VFS_LFSx(ilistdir_func)(size_t n_args, const mp_obj_t *args)
         path = vstr_null_terminated_str(&self->cur_dir);
     }
 
-    MP_VFS_LFSx(ilistdir_it_t) * iter = mp_obj_malloc(MP_VFS_LFSx(ilistdir_it_t), &mp_type_polymorph_iter);
+    MP_VFS_LFSx(ilistdir_it_t) * iter = m_new_obj_with_finaliser(MP_VFS_LFSx(ilistdir_it_t));
+    iter->base.type = &mp_type_polymorph_iter_with_finaliser;
+
     iter->iternext = MP_VFS_LFSx(ilistdir_it_iternext);
+    iter->finaliser = MP_VFS_LFSx(ilistdir_it_del);
     iter->is_str = is_str_type;
-    iter->vfs = self;
     int ret = LFSx_API(dir_open)(&self->lfs, &iter->dir, path);
     if (ret < 0) {
         mp_raise_OSError(-ret);
     }
+    iter->vfs = self;
     return MP_OBJ_FROM_PTR(iter);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(MP_VFS_LFSx(ilistdir_obj), 1, 2, MP_VFS_LFSx(ilistdir_func));