drivers/serial/uart_native_pty: Set PTY to be closed on exec

If the process does an exec() (or fork, or..) all descriptors are kept
open by default, unless O_CLOEXEC is set when opening them.
This is usefull for stdin/out/err so that new process is connected to
them, but it is very rare for it to be usefull for any other descriptor.

In general this leads to descriptors being kept open unnecessarily,
which either will block other process from getting them (for example
if the child survives the parent but it does something else).
Or for a "leak" which unnecessarily uses descriptors and memory in the
child process.

Let's ensure we do not leak it for this component as we do not need it.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

drivers/serial/uart_native_pty_bottom.c

@@ -139,7 +139,7 @@ int np_uart_open_pty(const char *uart_name, const char *auto_attach_cmd,
 	int ret;
 	int flags;
 
-	master_pty = posix_openpt(O_RDWR | O_NOCTTY);
+	master_pty = posix_openpt(O_RDWR | O_NOCTTY | O_CLOEXEC);
 	if (master_pty == -1) {
 		ERROR("Could not open a new PTY for the UART\n");
 	}
@@ -214,7 +214,7 @@ int np_uart_open_pty(const char *uart_name, const char *auto_attach_cmd,
 		 * The connection of the client would cause the HUP flag to be
 		 * cleared, and in turn set again at disconnect.
 		 */
-		ret = open(slave_pty_name, O_RDWR | O_NOCTTY);
+		ret = open(slave_pty_name, O_RDWR | O_NOCTTY | O_CLOEXEC);
 		if (ret == -1) {
 			err_nbr = errno;
 			ERROR("%s: Could not open terminal from the slave side (%i,%s)\n",