From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-patches@cygwin.com
Subject: [PATCH] Cygwin: pty: Fix race issue between closing and opening master.
Date: Fri, 14 Jan 2022 23:07:36 +0900 [thread overview]
Message-ID: <20220114140736.984-1-takashi.yano@nifty.ne.jp> (raw)
- 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;
}
--
2.34.1
reply other threads:[~2022-01-14 14:08 UTC|newest]
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