From 0d1fbfb755aa7856a8b94c74be2e116a0ca743cb Mon Sep 17 00:00:00 2001
From: Megamouse <studienricky89@googlemail.com>
Date: Thu, 25 Jan 2024 10:20:06 +0100
Subject: [PATCH] VFS: Fix some potential .back() segfaults

---
 Utilities/File.cpp                     |  2 +-
 rpcs3/Emu/vfs_config.cpp               | 33 +++++++++++++++++++-------
 rpcs3/rpcs3qt/vfs_dialog_usb_input.cpp |  1 +
 3 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/Utilities/File.cpp b/Utilities/File.cpp
index 36e762781c..b576992163 100644
--- a/Utilities/File.cpp
+++ b/Utilities/File.cpp
@@ -772,7 +772,7 @@ bool fs::create_path(const std::string& path)
 
 #ifdef _WIN32
 	// Workaround: don't call is_dir with naked drive letter
-	if (parent.size() < path.size() && parent.back() != ':' && !is_dir(parent) && !create_path(parent))
+	if (parent.size() < path.size() && (parent.empty() || (parent.back() != ':' && !is_dir(parent) && !create_path(parent))))
 #else
 	if (parent.size() < path.size() && !is_dir(parent) && !create_path(parent))
 #endif
diff --git a/rpcs3/Emu/vfs_config.cpp b/rpcs3/Emu/vfs_config.cpp
index 4ff5dd6659..c650bfaeeb 100644
--- a/rpcs3/Emu/vfs_config.cpp
+++ b/rpcs3/Emu/vfs_config.cpp
@@ -14,6 +14,20 @@ std::string cfg_vfs::get(const cfg::string& _cfg, std::string_view emu_dir) cons
 
 std::string cfg_vfs::get(const std::string& _cfg, const std::string& def, std::string_view emu_dir) const
 {
+	std::string path = _cfg;
+
+	// Fallback
+	if (path.empty())
+	{
+		if (def.empty())
+		{
+			vfs_log.notice("VFS config called with empty path and empty default");
+			return {};
+		}
+
+		path = def;
+	}
+
 	std::string _emu_dir; // Storage only
 
 	if (emu_dir.empty())
@@ -34,18 +48,14 @@ std::string cfg_vfs::get(const std::string& _cfg, const std::string& def, std::s
 		emu_dir = _emu_dir;
 	}
 
-	std::string path = _cfg;
-
-	if (path.empty())
-	{
-		// Fallback
-		path = def;
-	}
-
 	path = fmt::replace_all(path, "$(EmulatorDir)", emu_dir);
 
 	// Check if path does not end with a delimiter
-	if (path.back() != fs::delim[0] && path.back() != fs::delim[1])
+	if (path.empty())
+	{
+		vfs_log.error("VFS config path empty (_cfg='%s', def='%s', emu_dir='%s')", _cfg, def, emu_dir);
+	}
+	else if (path.back() != fs::delim[0] && path.back() != fs::delim[1])
 	{
 		path += '/';
 	}
@@ -74,6 +84,11 @@ cfg::device_info cfg_vfs::get_device_info(const cfg::device_entry& _cfg, std::st
 			def_path = def_it->second.path;
 		}
 
+		if (info.path.empty() && def_path.empty())
+		{
+			return info;
+		}
+
 		info.path = get(info.path, def_path, emu_dir);
 		return info;
 	}
diff --git a/rpcs3/rpcs3qt/vfs_dialog_usb_input.cpp b/rpcs3/rpcs3qt/vfs_dialog_usb_input.cpp
index b39a89c011..0f4970ee90 100644
--- a/rpcs3/rpcs3qt/vfs_dialog_usb_input.cpp
+++ b/rpcs3/rpcs3qt/vfs_dialog_usb_input.cpp
@@ -11,6 +11,7 @@ vfs_dialog_usb_input::vfs_dialog_usb_input(const QString& name, const cfg::devic
 	: QDialog(parent), m_gui_settings(std::move(_gui_settings)), m_gui_save(gui::fs_dev_usb_list)
 {
 	ensure(!!info);
+	ensure(!name.isEmpty());
 	ensure(name.back() >= '0' && name.back() <= '7');
 
 	setWindowTitle(tr("Edit %0").arg(name));