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

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: 3721a75 ("Cygwin: console: Make the console accessible from other terminals.") Reported-by: Kate Deplaix <[email protected]> Signed-off-by: Takashi Yano <[email protected]>
RTEMS · Mar 1, 2024 · c77a568 · c77a568
1 parent ee97ae1
commit c77a568
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diff --git 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;
 }

diff --git a/winsup/cygwin/release/3.5.2 b/winsup/cygwin/release/3.5.2
@@ -0,0 +1,7 @@
+Fixes:
+------
+
+- Fix the problem that console setup accesses shared memory which
+  is already unmapped due to race condition. To avoid this issue,
+  shared console memory will be kept mapped if it belongs to CTTY.
+  Addresses:  https://cygwin.com/pipermail/cygwin/2024-February/255561.html