Package: mutter Version: 51.0-3 Severity: serious Dear maintainers,
after upgrading mutter and gnome-shell to 51.0-3 (Debian sid, 2026-10-22), GDM can no longer start a greeter and the GNOME session crashes at startup on a system using the proprietary NVIDIA driver shipped in testing/sid (550.163.01-5.1). Symptoms - gdm retries until "GdmLocalDisplayFactory: maximum number of display failures reached. Giving up." - gnome-shell[3916]: segfault at ... ip ... sp ... error 4 in libmutter-cogl-51.so.0.0.0[5faf4] - [email protected]: Main process exited, code=killed, status=11/SEGV - GdmDisplay: Session never registered, failing Reproduction (deterministic, without GDM) $ gnome-shell --headless --mode=user; echo $? 139 $ gnome-shell --headless --mode=gdm; echo $? 139 strace shows the NVIDIA EGL/GBM stack being loaded (renderD129, nvidia-drm_gbm.so, libEGL_nvidia.so) followed by SIGSEGV. The faulting offset 0x5faf4 corresponds to cogl_renderer_is_hardware_accelerated(), which dereferences a NULL renderer. Upstream mutter 51 removed support for legacy NVIDIA drivers (NEWS 51.alpha, MR !5079); whether 550 counts as legacy is unclear, but mutter should not segfault when renderer/EGL initialization fails. System - Debian sid/testing (forky), kernel 7.1.13+deb14-amd64 - mutter 51.0-3, gnome-shell 51.0-3, gdm3 51.1-1 - nvidia-driver 550.163.01-5.1, GeForce RTX 3070 Ti Laptop GPU - Downgrading mutter/gnome-shell to 50.5-1 (testing) makes GNOME work again Impact 550.163.01 is the newest nvidia-driver in testing and sid; 555.58.02 has been in experimental since 2024. When mutter 51 migrates to testing, GNOME will be unusable for users of the packaged NVIDIA driver. Please consider: 1. keeping mutter 51 out of testing until a compatible driver is available, or 2. adding a versioned Breaks/Conflicts against nvidia-driver (<< 555) so apt cannot install the broken combination, and/or 3. fixing the NULL dereference so an EGL failure degrades gracefully instead of killing gnome-shell. Thanks, Claudio Giordano
