tty: don't restore locking with --unprivileged

[rst0git]

TIOCSLCKTRMIOS requires CAP_SYS_ADMIN. This causes criu restore to fail when used with --unprivileged.

[codecov-commenter]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.05% ⚠️

Comparison is base (72494ed) 70.65% compared to head (37b9396) 70.60%.

❗ Current head 37b9396 differs from pull request most recent head 2e84b58. Consider uploading reports for the commit 2e84b58 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##           criu-dev    #2238      +/-   ##
============================================
- Coverage     70.65%   70.60%   -0.05%     
============================================
  Files           133      133              
  Lines         33317    33320       +3     
============================================
- Hits          23540    23527      -13     
- Misses         9777     9793      +16     

Files Changed	Coverage Δ
criu/tty.c	77.46% <66.66%> (+0.02%)	⬆️

... and 6 files with indirect coverage changes

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[avagin]

Pls add a full description what this ioctl is about and why it is safe to do what you are doing in this patch.

[avagin]

@rst0git ping

[rst0git]

Pls add a full description what this ioctl is about and why it is safe to do what you are doing in this patch.

Thank you for the question. I investigated this further and while skipping TIOCSLCKTRMIOS for unprivileged restore seems to work, it might not be safe. Instead, it seems that allowing CAP_CHECKPOINT_RESTORE to be used with TIOCSLCKTRMIOS is more appropriate.