From 31db9f401955b439cf0013e7a0c8bc1334a42efd Mon Sep 17 00:00:00 2001 From: Takashi Yano Date: Fri, 14 Jan 2022 19:35:12 +0900 Subject: [PATCH] Cygwin: pty: Fix race issue between closing and opening master. - If the from_master is closed before cleaning up other pipes, such as from_slave_nat, the same pty may be allocated and pty master may try to open the pipe which is not closed yet, and it will fail. This patch fixes the issue. --- winsup/cygwin/fhandler_tty.cc | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc index 1ae4edd63..7bef6958c 100644 --- a/winsup/cygwin/fhandler_tty.cc +++ b/winsup/cygwin/fhandler_tty.cc @@ -2146,8 +2146,6 @@ fhandler_pty_master::close () if (!ForceCloseHandle (from_master_nat)) termios_printf ("error closing from_master_nat %p, %E", from_master_nat); - if (!ForceCloseHandle (from_master)) - termios_printf ("error closing from_master %p, %E", from_master); if (!ForceCloseHandle (to_master_nat)) termios_printf ("error closing to_master_nat %p, %E", to_master_nat); from_master_nat = to_master_nat = NULL; @@ -2156,7 +2154,7 @@ fhandler_pty_master::close () from_slave_nat = NULL; if (!ForceCloseHandle (to_master)) termios_printf ("error closing to_master %p, %E", to_master); - to_master = from_master = NULL; + to_master = NULL; ForceCloseHandle (echo_r); ForceCloseHandle (echo_w); echo_r = echo_w = NULL; @@ -2171,6 +2169,12 @@ fhandler_pty_master::close () termios_printf ("CloseHandle (input_available_event<%p>), %E", input_available_event); + /* The from_master must be closed last so that the same pty is not + allocated before cleaning up the other corresponding instances. */ + if (!ForceCloseHandle (from_master)) + termios_printf ("error closing from_master %p, %E", from_master); + from_master = NULL; + return 0; } @@ -3069,12 +3073,14 @@ err: close_maybe (output_mutex); close_maybe (input_mutex); close_maybe (from_master_nat); - close_maybe (from_master); close_maybe (to_master_nat); close_maybe (to_master); close_maybe (echo_r); close_maybe (echo_w); close_maybe (master_ctl); + /* The from_master must be closed last so that the same pty is not + allocated before cleaning up the other corresponding instances. */ + close_maybe (from_master); termios_printf ("pty%d open failed - failed to create %s", unit, errstr); return false; }