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, 18 insertions, 1 deletions

diff --git a/extmod/vfs_posix.c b/extmod/vfs_posix.c
index 9b0036581..36b211b84 100644
--- a/extmod/vfs_posix.c
+++ b/extmod/vfs_posix.c
@@ -33,6 +33,10 @@
 
 #if MICROPY_VFS_POSIX
 
+#if !MICROPY_ENABLE_FINALISER
+#error "MICROPY_VFS_POSIX requires MICROPY_ENABLE_FINALISER"
+#endif
+
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -162,6 +166,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(vfs_posix_getcwd_obj, vfs_posix_getcwd);
 typedef struct _vfs_posix_ilistdir_it_t {
     mp_obj_base_t base;
     mp_fun_1_t iternext;
+    mp_fun_1_t finaliser;
     bool is_str;
     DIR *dir;
 } vfs_posix_ilistdir_it_t;
@@ -226,10 +231,22 @@ STATIC mp_obj_t vfs_posix_ilistdir_it_iternext(mp_obj_t self_in) {
     }
 }
 
+STATIC mp_obj_t vfs_posix_ilistdir_it_del(mp_obj_t self_in) {
+    vfs_posix_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
+    if (self->dir != NULL) {
+        MP_THREAD_GIL_EXIT();
+        closedir(self->dir);
+        MP_THREAD_GIL_ENTER();
+    }
+    return mp_const_none;
+}
+
 STATIC mp_obj_t vfs_posix_ilistdir(mp_obj_t self_in, mp_obj_t path_in) {
     mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
-    vfs_posix_ilistdir_it_t *iter = mp_obj_malloc(vfs_posix_ilistdir_it_t, &mp_type_polymorph_iter);
+    vfs_posix_ilistdir_it_t *iter = m_new_obj_with_finaliser(vfs_posix_ilistdir_it_t);
+    iter->base.type = &mp_type_polymorph_iter_with_finaliser;
     iter->iternext = vfs_posix_ilistdir_it_iternext;
+    iter->finaliser = vfs_posix_ilistdir_it_del;
     iter->is_str = mp_obj_get_type(path_in) == &mp_type_str;
     const char *path = vfs_posix_get_path_str(self, path_in);
     if (path[0] == '\0') {