mountmgr.sys: Do a device check before returning a default serial port name.

dlls/mountmgr.sys/device.c

@@ -1865,7 +1865,7 @@ static BOOL create_port_device( DRIVER_OBJECT *driver, int n, const char *unix_p
     UNICODE_STRING nt_name, symlink_name, default_name;
     DEVICE_OBJECT *dev_obj;
     NTSTATUS status;
-    struct set_dosdev_symlink_params params = { dosdevices_path, unix_path };
+    struct set_dosdev_symlink_params params = { dosdevices_path, unix_path, driver == serial_driver };
 
     /* create DOS device */
     if (MOUNTMGR_CALL( set_dosdev_symlink, &params )) return FALSE;

dlls/mountmgr.sys/unixlib.c

@@ -46,6 +46,7 @@
 #ifdef HAVE_SYS_MOUNT_H
 #include <sys/mount.h>
 #endif
+#include <termios.h>
 
 #include "unixlib.h"
 
@@ -268,6 +269,27 @@ static NTSTATUS set_dosdev_symlink( void *args )
     char *path;
     NTSTATUS status = STATUS_SUCCESS;
 
+#ifdef linux
+    /* Serial port device files almost always exist on Linux even if the corresponding serial
+     * ports don't exist. Do a basic functionality check before advertising a serial port. */
+    if (params->serial)
+    {
+        struct termios tios;
+        int fd;
+
+        if ((fd = open( params->dest, O_RDONLY )) == -1)
+            return FALSE;
+
+        if (tcgetattr( fd, &tios ) == -1)
+        {
+            close( fd );
+            return FALSE;
+        }
+
+        close( fd );
+    }
+#endif
+
     if (!(path = get_dosdevices_path( params->dev ))) return STATUS_NO_MEMORY;
 
     if (params->dest && params->dest[0])

dlls/mountmgr.sys/unixlib.h

@@ -75,6 +75,7 @@ struct set_dosdev_symlink_params
 {
     const char *dev;
     const char *dest;
+    BOOL serial;
 };
 
 struct get_volume_dos_devices_params