server: Avoid a crash when trying to wait on a disconnected pipe client.

server/fd.c

@@ -1710,6 +1710,12 @@ void set_fd_signaled( struct fd *fd, int signaled )
     if (signaled) wake_up( fd->user, 0 );
 }
 
+/* set or clear the fd signaled state */
+int is_fd_signaled( struct fd *fd )
+{
+    return fd->signaled;
+}
+
 /* handler for close_handle that refuses to close fd-associated handles in other processes */
 int fd_close_handle( struct object *obj, struct process *process, obj_handle_t handle )
 {

server/file.h

@@ -70,6 +70,7 @@ extern void set_fd_events( struct fd *fd, int events );
 extern obj_handle_t lock_fd( struct fd *fd, file_pos_t offset, file_pos_t count, int shared, int wait );
 extern void unlock_fd( struct fd *fd, file_pos_t offset, file_pos_t count );
 extern void set_fd_signaled( struct fd *fd, int signaled );
+extern int is_fd_signaled( struct fd *fd );
 
 extern int default_fd_signaled( struct object *obj, struct thread *thread );
 extern unsigned int default_fd_map_access( struct object *obj, unsigned int access );

server/named_pipe.c

@@ -176,6 +176,7 @@ static const struct fd_ops pipe_server_fd_ops =
 
 /* client end functions */
 static void pipe_client_dump( struct object *obj, int verbose );
+static int pipe_client_signaled( struct object *obj, struct thread *thread );
 static struct fd *pipe_client_get_fd( struct object *obj );
 static void pipe_client_destroy( struct object *obj );
 static void pipe_client_flush( struct fd *fd, struct event **event );
@@ -188,7 +189,7 @@ static const struct object_ops pipe_client_ops =
     no_get_type,                  /* get_type */
     add_queue,                    /* add_queue */
     remove_queue,                 /* remove_queue */
-    default_fd_signaled,          /* signaled */
+    pipe_client_signaled,         /* signaled */
     no_satisfied,                 /* satisfied */
     no_signal,                    /* signal */
     pipe_client_get_fd,           /* get_fd */
@@ -289,6 +290,13 @@ static void pipe_client_dump( struct object *obj, int verbose )
     fprintf( stderr, "Named pipe client server=%p\n", client->server );
 }
 
+static int pipe_client_signaled( struct object *obj, struct thread *thread )
+{
+    struct pipe_client *client = (struct pipe_client *) obj;
+
+    return client->fd && is_fd_signaled(client->fd);
+}
+
 static void named_pipe_destroy( struct object *obj)
 {
     struct named_pipe *pipe = (struct named_pipe *) obj;