Clipboard integration on libweston may cause race condition and crash the weston process

[tumugin]

Windows build number:

10.0.26220.0

Your Distribution version:

Ubuntu 24.04.3 LTS

Your WSL versions:

WSL バージョン: 2.7.0.0
カーネル バージョン: 6.6.114.1-1
WSLg バージョン: 1.0.71
MSRDC バージョン: 1.2.6676
Direct3D バージョン: 1.611.1-81528511
DXCore バージョン: 10.0.26100.1-240331-1435.ge-release
Windows バージョン: 10.0.26220.7344

Steps to reproduce:

• Open gnome-terminal on Linux side with WSLg.
• Open Microsoft Edge on Windows side and copy some text from the website.
  • I could reproduce on Google. I typed some text on the search bar in the website and copied the text.
  • When copying, use Ctrl+C and hit the key combination for 10 to 20 times as fast as you can

WSL logs:

weston.log before the crash

[04:34:55.967] read fd:127 12 (available 65536, mask 0x5)
[04:34:55.967] nothing happened, buffered the bytes
[04:34:55.967] read fd:127 0 (available 131060, mask 0x4)
[04:34:55.967] non-incr transfer read complete
[04:34:56.106] xfixes selection notify event: owner 2097153
[04:34:56.106] our window, skipping
[04:34:56.107] selection request, CLIPBOARD, target UTF8_STRING, property FCITX_X11_SEL_CLIPBOARD
[04:34:56.107]


RDP clipboard_data_source_send new (0x782208000b80:received data:fd 130) vs prev (0x782208000b80:received data:fd 126): outstanding RDP data request (client to server)

stderr.log after the crash

weston: ../libweston/backend-rdp/rdpclip.c:967: clipboard_data_source_write: Assertion `source->data_source_fd == fd' failed.
(EE)[04:28:19.011] <5>WSLGd: Run:110:  pid 14 terminated with signal 6, /usr/bin/sh -c /usr/bin/weston --backend=rdp-backend.so --modules=wslgd-notify.so --xwayland --socket=wayland-0 --shell=rdprail-shell.so --log=/mnt/wslg/weston.log --logger-scopes=log,rdp-backend,rdprail-shell failed to write to XWayland fd: Broken pipe

WSL dumps:

No response

Expected behavior:

No response

Actual behavior:

Weston will crash and the Linux GUI apps will stop running.

[tumugin]

I actually found this bug when I was using IntelliJ IDEA with the IdeaVim plugin. I was copying some text from the browser on the Windows side and pasting it into IDEA, and then the WSLg crashed.
This issue might be related to #589.

Actually, IDEA wasn't needed to make this problem happen, and just using 'gnome-terminal' was enough. I couldn't recreate the issue with 'gnome-text-editor', so it's possible that the application's clipboard functionality is causing the problem.

[tumugin]

I checked the code for libweston and the part that causes the crash (https://github.com/microsoft/weston-mirror/blob/working/libweston/backend-rdp/rdpclip.c#L967). Would it be enough to write 'goto fail;' or 'return 0;' when this assertion fails?

[cubimon]

thanks for finding this out, I get this error quite often too. Do you know how to build/run wslg on windows with libweston with this fix?

[tumugin]

I believe it will involve building a modified WSLg system distribution that includes libweston, but I haven't had time to try it yet.