tree-wide: acquire /dev/console lock around any attempts to reset TTY

src/basic/terminal-util.c

@@ -599,6 +599,10 @@ void reset_dev_console_fd(int fd, bool switch_to_text) {
 
         assert(fd >= 0);
 
+        _cleanup_close_ int lock_fd = lock_dev_console();
+        if (lock_fd < 0)
+                log_debug_errno(lock_fd, "Failed to lock /dev/console, ignoring: %m");
+
         r = terminal_reset_ioctl(fd, switch_to_text);
         if (r < 0)
                 log_warning_errno(r, "Failed to reset /dev/console, ignoring: %m");
@@ -1592,6 +1596,16 @@ int terminal_reset_defensive(int fd, bool switch_to_text) {
         return r;
 }
 
+int terminal_reset_defensive_locked(int fd, bool switch_to_text) {
+        assert(fd >= 0);
+
+        _cleanup_close_ int lock_fd = lock_dev_console();
+        if (lock_fd < 0)
+                log_debug_errno(lock_fd, "Failed to acquire lock for /dev/console, ignoring: %m");
+
+        return terminal_reset_defensive(fd, switch_to_text);
+}
+
 void termios_disable_echo(struct termios *termios) {
         assert(termios);
 

src/basic/terminal-util.h

@@ -30,6 +30,7 @@
 bool isatty_safe(int fd);
 
 int terminal_reset_defensive(int fd, bool switch_to_text);
+int terminal_reset_defensive_locked(int fd, bool switch_to_text);
 
 int terminal_set_cursor_position(int fd, unsigned row, unsigned column);