If you disable the mouse pointer from within ThinLinc, then the entire session crashes with this in the log: > (EE) > (EE) Backtrace: > (EE) 0: /opt/thinlinc/libexec/Xvnc (xorg_backtrace+0x41) [0x76d921] > (EE) 1: /opt/thinlinc/libexec/Xvnc (0x400000+0x370f29) [0x770f29] > (EE) 2: /lib64/libc.so.6 (0x7fd160482000+0x1a090) [0x7fd16049c090] > (EE) 3: /opt/thinlinc/libexec/Xvnc (miPointerGetPosition+0x87) [0x75d927] > (EE) 4: /opt/thinlinc/libexec/Xvnc (vncGetPointerPos+0x32) [0x593312] > (EE) 5: /opt/thinlinc/libexec/Xvnc (_ZN14XserverDesktop12blockHandlerEPi+0xea) [0x591a7a] > (EE) 6: /opt/thinlinc/libexec/Xvnc (vncCallBlockHandlers+0x27) [0x5864b7] > (EE) 7: /opt/thinlinc/libexec/Xvnc (BlockHandler+0x56) [0x723706] > (EE) 8: /opt/thinlinc/libexec/Xvnc (WaitForSomething+0xc5) [0x76b9d5] > (EE) 9: /opt/thinlinc/libexec/Xvnc (Dispatch+0xac) [0x71ecec] > (EE) 10: /opt/thinlinc/libexec/Xvnc (dix_main+0x388) [0x722dd8] > (EE) 11: /lib64/libc.so.6 (0x7fd160482000+0x3248) [0x7fd160485248] > (EE) 12: /lib64/libc.so.6 (__libc_start_main+0x8b) [0x7fd16048530b] > (EE) 13: /opt/thinlinc/libexec/Xvnc (0x400000+0xc4220) [0x4c4220] > (EE) > (EE) Segmentation fault at address 0x2c > (EE) > Fatal server error: > (EE) Caught signal 11 (Segmentation fault). Server aborting > (EE) This can easily be provoked by doing: > $ xinput set-int-prop 6 117 8 0 (this changes the property "enabled" for the VNC pointer device to 0) It is also available in the GUI in (at least) Xfce, where they have a checkbox for it. This is a regression from 4.17.0, where this crash cannot be observed. This issue was originally reported upstream: https://github.com/TigerVNC/tigervnc/pull/1894
It is unclear what caused this regression. It seems to have something to do with floating devices. But the bug cannot be triggered on 4.17.0 by setting the pointer device to be floating. This is the most likely candidate I can find, given the range of commits between the broken and working state: https://gitlab.freedesktop.org/xorg/xserver/-/commit/5c4816afa7722ea47d1a7dea983a953e7b454d26
That was a red herring. A git bisect showed that the issue is indeed connected to disabling the device. Specifically: https://gitlab.freedesktop.org/xorg/xserver/-/commit/8b75ec34dfbe435cd3a17e64138e22a37395a6d8
I have verified that the session doesn't crash when mouse is disabled with a post xorg-server upgrade build of the ThinLinc server: I installed GNOME and Xfce4 on a RHEL9 machine and compared 4.18.0 to 4.18.0post (3920). * ThinLinc server 4.18.0; When toggling mouse off in the Xfce settings or via the xinput command, the session's xorg-server immediately crashes with the backtrace seen in comment 0. What's even more unfortunate is that the setting has been persisted, such that subsequent attempts to start a session will fail with the same type of crash. When in this broken state, the user can start sessions again after upgrading to 4.18.0post. * Thinlinc server 4.18.0post; When toggling mouse off, mouse is disabled and the session is still running as expected.
> MUST: > * The session shouldn't crash when mouse is disabled. The session, and its xorg-server, no longer crash when mouse is disabled post upgrade (v21.1.13 -> v21.1.14). Closing.
