um: chan_xterm: Fix fd leak

xterm serial channel was leaking a fd used in setting up the
port helper

This bug is prehistoric - it predates switching to git. The "fixes"
header here is really just to mark all the versions we would like this to
apply to which is "Anything from the Cretaceous period onwards".

No dinosaurs were harmed in fixing this bug.

Fixes: b40997b872 ("um: drivers/xterm.c: fix a file descriptor leak")
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/xterm.c

@@ -18,6 +18,7 @@
 struct xterm_chan {
 	int pid;
 	int helper_pid;
+	int chan_fd;
 	char *title;
 	int device;
 	int raw;
@@ -33,6 +34,7 @@ static void *xterm_init(char *str, int device, const struct chan_opts *opts)
 		return NULL;
 	*data = ((struct xterm_chan) { .pid 		= -1,
 				       .helper_pid 	= -1,
+				       .chan_fd		= -1,
 				       .device 		= device,
 				       .title 		= opts->xterm_title,
 				       .raw  		= opts->raw } );
@@ -149,6 +151,7 @@ static int xterm_open(int input, int output, int primary, void *d,
 		goto out_kill;
 	}
 
+	data->chan_fd = fd;
 	new = xterm_fd(fd, &data->helper_pid);
 	if (new < 0) {
 		err = new;
@@ -206,6 +209,8 @@ static void xterm_close(int fd, void *d)
 		os_kill_process(data->helper_pid, 0);
 	data->helper_pid = -1;
 
+	if (data->chan_fd != -1)
+		os_close_file(data->chan_fd);
 	os_close_file(fd);
 }