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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.
This commit is contained in:
Takashi Yano 2022-01-14 19:35:12 +09:00
parent bff4594b08
commit 909ed837cc
1 changed files with 10 additions and 4 deletions
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14
winsup/cygwin/fhandler_tty.cc
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@ -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;
}