[newlib-cygwin/cygwin-3_5-branch] Cygwin: console: Do not unmap shared console memory belonging to ctty.
Takashi Yano
tyan0@sourceware.org
Fri Mar 1 11:01:47 GMT 2024
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=cf121e088f928c68a8e3c799db97478c89b6dd96
commit cf121e088f928c68a8e3c799db97478c89b6dd96
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Fri Mar 1 19:05:36 2024 +0900
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: 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>
Diff:
---
winsup/cygwin/fhandler/console.cc | 8 +++++---
winsup/cygwin/release/3.5.2 | 7 +++++++
2 files changed, 12 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;
}
diff --git a/winsup/cygwin/release/3.5.2 b/winsup/cygwin/release/3.5.2
new file mode 100644
index 000000000..7d8df9489
--- /dev/null
+++ 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
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