[PATCH] Cygwin: console: Do not unmap shared console memory belonging to ctty.

[Takashi Yano]

In the condition that console setup for CTTY and close run at the
sametime, accessing shared console memory which is already unmapped
may occur. With this patch, to avoid this race issue, shared console
memory which belongs to contorolling terminal (CTTY) is kept mapped
as before.
Addresses: https://cygwin.com/pipermail/cygwin/2024-February/255561.html

Fixes: 3721a756b0d8 ("Cygwin: console: Make the console accessible from other terminals.")
Reported-by: Kate Deplaix <kit-ty-kate@outlook.com>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/fhandler/console.cc | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/fhandler/console.cc b/winsup/cygwin/fhandler/console.cc
index c16ca3962..67ea95466 100644
--- a/winsup/cygwin/fhandler/console.cc
+++ b/winsup/cygwin/fhandler/console.cc
@@ -1926,9 +1926,11 @@ fhandler_console::close ()
 	  || get_device () == (dev_t) myself->ctty))
     free_console ();
 
-  if (shared_console_info[unit])
-    UnmapViewOfFile ((void *) shared_console_info[unit]);
-  shared_console_info[unit] = NULL;
+  if (shared_console_info[unit] && myself->ctty != tc ()->ntty)
+    {
+      UnmapViewOfFile ((void *) shared_console_info[unit]);
+      shared_console_info[unit] = NULL;
+    }
 
   return 0;
 }
-- 
2.43.0