Package: kwin-wayland Version: 4:6.3.6-1 Severity: important Tags: patch fixed-upstream trixie Control: forwarded -1 https://bugs.kde.org/show_bug.cgi?id=504959
Dear Maintainer, kwin_wayland 6.3.6 in trixie crashes with SIGSEGV when external monitors are removed, taking down the whole Plasma session. On my machine this happens when unplugging a Thunderbolt dock with two monitors attached. Cause: wl_output removal is racy. A client (Firefox, Chromium, Electron apps, anything using wp_color_manager_v1) can send wp_color_manager_v1.get_output for a wl_output whose backing output KWin has already removed. ColorManagerV1::wp_color_manager_v1_get_output() then calls OutputInterface::get(output)->handle(), which is null, and the ColorManagementOutputV1 constructor dereferences it (src/wayland/colormanagement_v1.cpp:580 in 6.3.6). Key frames from the symbolized backtrace of the first crash (client was firefox-esr; core no longer available): #4 KWin::ColorManagementOutputV1::ColorManagementOutputV1(wl_client*, uint, uint, KWin::Output*) (output=0x0) at src/wayland/colormanagement_v1.cpp:580 ... libffi / libwayland-server #10 wl_event_loop_dispatch #11 KWin::Display::dispatchEvents() All three crashes fault at the same address (libkwin.so.6 + 0x5a8130). Closing Firefox before unplugging does not avoid it, since other clients send the same request. Upstream fix (KDE bug 504959, fixed in 6.4.5), two small commits: e1fd647b979df7f0bd10065932a614a2aa806e87 wayland: Make ColorManagementOutputV1 handle output removal better https://invent.kde.org/plasma/kwin/-/commit/e1fd647b979df7f0bd10065932a614a2aa806e87 172f8f2e71d93a27f23586587d9cf86cbfee8615 wayland: Check for nullptr output in ColorManagementOutputV1 https://invent.kde.org/plasma/kwin/-/commit/172f8f2e71d93a27f23586587d9cf86cbfee8615 (Cherry-picked to Plasma/6.4 as 598438b9 and 5baacbef.) Both only touch src/wayland/colormanagement_v1.{cpp,h}, which is the same code that 6.3.6 ships, so they should backport cleanly. Could these be included in a trixie point release? This report was drafted with an AI assistant (Claude Opus 5.5). The crashes, versions and backtraces are from my system; I checked that the upstream patches apply to the 6.3.6 source. System: Debian 13 (trixie), amd64, kernel 6.12.113+deb13-amd64 kwin-wayland 4:6.3.6-1 libqt6core6t64 6.8.2+dfsg-9+deb13u2 libwayland-server0 1.23.1-3 Hardware: Dell XPS 15 9510 (Intel + NVIDIA), Dell SD25TB4 dock Thanks!
