From 565f7183aab390986e678dfb909e2481e94e441f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Verschelde?= <rverschelde@gmail.com>
Date: Thu, 31 Oct 2019 15:14:49 +0100
Subject: [PATCH] Prevent crash when we can't write to editor cache or config
 path

This can happen if users somehow got wrong user permissions assigned to
their Godot cache, config or data paths (e.g. `~/.config/godot`).

The error messages should give them a hint as to what the issue may be.

Fixes #33199.

There may be other situations that still lead to a crash, we need to
review all uses of `FileAccess::open` with `FileAccess::WRITE` mode to
ensure that proper pointer validation is done.
---
 editor/editor_file_system.cpp      | 15 +++++++--------
 editor/editor_resource_preview.cpp | 21 +++++++++++++--------
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/editor/editor_file_system.cpp b/editor/editor_file_system.cpp
index 3663bdee279..2467e1f722a 100644
--- a/editor/editor_file_system.cpp
+++ b/editor/editor_file_system.cpp
@@ -325,14 +325,12 @@ void EditorFileSystem::_save_filesystem_cache() {
 	String fscache = EditorSettings::get_singleton()->get_project_settings_dir().plus_file(CACHE_FILE_NAME);
 
 	FileAccess *f = FileAccess::open(fscache, FileAccess::WRITE);
-	if (f == NULL) {
-		ERR_PRINTS("Error writing fscache '" + fscache + "'.");
-	} else {
-		f->store_line(filesystem_settings_version_for_import);
-		_save_filesystem_cache(filesystem, f);
-		f->close();
-		memdelete(f);
-	}
+	ERR_FAIL_COND_MSG(!f, "Cannot create file '" + fscache + "'. Check user write permissions.");
+
+	f->store_line(filesystem_settings_version_for_import);
+	_save_filesystem_cache(filesystem, f);
+	f->close();
+	memdelete(f);
 }
 
 void EditorFileSystem::_thread_func(void *_userdata) {
@@ -1373,6 +1371,7 @@ void EditorFileSystem::_save_late_updated_files() {
 	//files that already existed, and were modified, need re-scanning for dependencies upon project restart. This is done via saving this special file
 	String fscache = EditorSettings::get_singleton()->get_project_settings_dir().plus_file("filesystem_update4");
 	FileAccessRef f = FileAccess::open(fscache, FileAccess::WRITE);
+	ERR_FAIL_COND_MSG(!f, "Cannot create file '" + fscache + "'. Check user write permissions.");
 	for (Set<String>::Element *E = late_update_files.front(); E; E = E->next()) {
 		f->store_line(E->get());
 	}
diff --git a/editor/editor_resource_preview.cpp b/editor/editor_resource_preview.cpp
index 65a17047703..55f93470459 100644
--- a/editor/editor_resource_preview.cpp
+++ b/editor/editor_resource_preview.cpp
@@ -201,9 +201,8 @@ void EditorResourcePreview::_generate_preview(Ref<ImageTexture> &r_texture, Ref<
 			if (has_small_texture) {
 				ResourceSaver::save(cache_base + "_small.png", r_small_texture);
 			}
-			Error err;
-			FileAccess *f = FileAccess::open(cache_base + ".txt", FileAccess::WRITE, &err);
-			ERR_FAIL_COND_MSG(err != OK, "Cannot create file '" + cache_base + ".txt'.");
+			FileAccess *f = FileAccess::open(cache_base + ".txt", FileAccess::WRITE);
+			ERR_FAIL_COND_MSG(!f, "Cannot create file '" + cache_base + ".txt'. Check user write permissions.");
 			f->store_line(itos(thumbnail_size));
 			f->store_line(itos(has_small_texture));
 			f->store_line(itos(FileAccess::get_modified_time(p_item.path)));
@@ -295,11 +294,17 @@ void EditorResourcePreview::_thread() {
 								//update modified time
 
 								f = FileAccess::open(file, FileAccess::WRITE);
-								f->store_line(itos(thumbnail_size));
-								f->store_line(itos(has_small_texture));
-								f->store_line(itos(modtime));
-								f->store_line(md5);
-								memdelete(f);
+								if (!f) {
+									// Not returning as this would leave the thread hanging and would require
+									// some proper cleanup/disabling of resource preview generation.
+									ERR_PRINTS("Cannot create file '" + file + "'. Check user write permissions.");
+								} else {
+									f->store_line(itos(thumbnail_size));
+									f->store_line(itos(has_small_texture));
+									f->store_line(itos(modtime));
+									f->store_line(md5);
+									memdelete(f);
+								}
 							}
 						} else {
 							memdelete(f);