xwayland: minor fixups for stability (#8323)

* xwayland: add inline safe closing of fds and fix LOCK_FILE_MODE permissions

* xwayland: auto recreate xwayland instance if it crashes

* xwayland: delay auto-restart until later

src/xwayland/Server.cpp

@@ -30,7 +30,7 @@
 constexpr int SOCKET_DIR_PERMISSIONS = 0755;
 constexpr int SOCKET_BACKLOG         = 1;
 constexpr int MAX_SOCKET_RETRIES     = 32;
-constexpr int LOCK_FILE_MODE         = 044;
+constexpr int LOCK_FILE_MODE         = 0444;
 
 static bool   setCloseOnExec(int fd, bool cloexec) {
     int flags = fcntl(fd, F_GETFD);
@@ -58,6 +58,11 @@ void cleanUpSocket(int fd, const char* path) {
         unlink(path);
 }
 
+inline void closeSocketSafely(int& fd) {
+    if (fd >= 0)
+        close(fd);
+}
+
 static int createSocket(struct sockaddr_un* addr, size_t path_size) {
     socklen_t size = offsetof(struct sockaddr_un, sun_path) + path_size + 1;
     int       fd   = socket(AF_UNIX, SOCK_STREAM, 0);
@@ -252,8 +257,8 @@ CXWaylandServer::~CXWaylandServer() {
     if (display < 0)
         return;
 
-    close(xFDs[0]);
-    close(xFDs[1]);
+    closeSocketSafely(xFDs[0]);
+    closeSocketSafely(xFDs[1]);
 
     std::string lockPath = std::format("/tmp/.X{}-lock", display);
     safeRemove(lockPath);
@@ -283,14 +288,10 @@ void CXWaylandServer::die() {
     if (pipeFd >= 0)
         close(pipeFd);
 
-    if (waylandFDs[0] >= 0)
-        close(waylandFDs[0]);
-    if (waylandFDs[1] >= 0)
-        close(waylandFDs[1]);
-    if (xwmFDs[0] >= 0)
-        close(xwmFDs[0]);
-    if (xwmFDs[1] >= 0)
-        close(xwmFDs[1]);
+    closeSocketSafely(waylandFDs[0]);
+    closeSocketSafely(waylandFDs[1]);
+    closeSocketSafely(xwmFDs[0]);
+    closeSocketSafely(xwmFDs[1]);
 
     // possible crash. Better to leak a bit.
     //if (xwaylandClient)
@@ -407,7 +408,7 @@ bool CXWaylandServer::start() {
 
     close(notify[1]);
     close(waylandFDs[1]);
-    close(xwmFDs[1]);
+    closeSocketSafely(xwmFDs[1]);
     waylandFDs[1] = -1;
     xwmFDs[1]     = -1;
 

src/xwayland/XWM.cpp

@@ -13,6 +13,7 @@
 #include "../defines.hpp"
 #include "../Compositor.hpp"
 #include "../protocols/core/Seat.hpp"
+#include "../managers/eventLoop/EventLoopManager.hpp"
 #include "../managers/SeatManager.hpp"
 #include "../protocols/XWaylandShell.hpp"
 #include "../protocols/core/Compositor.hpp"
@@ -691,6 +692,8 @@ int CXWM::onEvent(int fd, uint32_t mask) {
         Debug::log(CRIT, "XWayland has yeeten the xwm off?!");
         g_pXWayland->pWM.reset();
         g_pXWayland->pServer.reset();
+        // Attempt to create fresh instance
+        g_pEventLoopManager->doLater([]() { g_pXWayland = std::make_unique<CXWayland>(true); });
         return 0;
     }