Hi Larry and Jason,
I am from VirtualBox team. I noticed your conversation here:
https://lore.kernel.org/lkml/Ym8uPcuQpq1xBS6d@xxxxxxxxx/T/#mea7aa731b5524a05ac3b3e8588c0c42235bb33d6 <https://lore.kernel.org/lkml/Ym8uPcuQpq1xBS6d@xxxxxxxxx/T/#mea7aa731b5524a05ac3b3e8588c0c42235bb33d6>
Please let me add my 5c. I agree with Larry, the issue start happen after 6e8ec2552c7d. I did not do complete bisecting, but rather tried this revision and the one before (with dcd03ba15947cbad1a34cfed370c4feb41058469 -- I do not see the issue).
For me this issue is quite reproducible with Ubuntu 20.04 Linux guest (other guests are also affected). It happens even if there is no VBox Guest Additions installed into guest. Guest kernel version does not play much role. Running kernel 5.18-rc1+ on the host side is essential.
The first way for me to reproduce it -- is to run stress-ng(1) tool inside guest and perform random mouse cursor movements (basically, mouse or keyboard interrupts generation is somehow essential here). Tool will report the following error:
root@test-VirtualBox:~# stress-ng --vm 4 -t 10
stress-ng: info: [5463] dispatching hogs: 4 vm
stress-ng: fail: [5464] stress-ng-vm: detected 194065152 bit errors while stressing memory
stress-ng: error: [5463] process 5464 (stress-ng-vm) terminated with an error, exit status=1 (stress-ng core failure)
stress-ng: info: [5463] unsuccessful run completed in 10.06s
This approach does not work in 100% cases, but triggers issue quite frequently.
The second approach is much more reliable for me. I basically, start compiling kernel inside guest (say, with make -j4) and start moving mouse (or generate keyboard interrupts, pressing keys randomly). In this case, gcc processes will randomly receive SEGFAULT.
Important note: if I do not touch mouse or keyboard in both cases above -- all works as normal.
My initial guess was that this might have something to do with kstack randomization, but booting host kernel with randomize_kstack_offset=0 seem does not change anything in this regard.
I am currently running out of ideas what exactly might trigger such behavior. Hopefully, this additional info might shed additional light.
Best regards,
Vadim