tty: skip ioctl(TIOCSLCKTRMIOS) if possible #2311
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If ioctl(TIOCSLCKTRMIOS) fails with EPERM it means that a CRIU process lacks of CAP_SYS_ADMIN capability. But we can use ioctl(TIOCGLCKTRMIOS) to *read* current ->termios_locked value from the kernel and if it's the same as we already have we can skip failing ioctl(TIOCSLCKTRMIOS) safely. Adrian has recently posted [1] a very good patch to allow ioctl(TIOCSLCKTRMIOS) for processes that have CAP_CHECKPOINT_RESTORE (right now it requires CAP_SYS_ADMIN). [1] https://lore.kernel.org/all/20231206134340.7093-1-areber@redhat.com/ Suggested-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
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I have tested this with the example from our wiki (https://criu.org/Simple_loop#A_shell_job): And it works perfectly fine for this case. |
Codecov ReportAttention:
Additional details and impacted files@@ Coverage Diff @@
## criu-dev #2311 +/- ##
============================================
- Coverage 70.86% 70.85% -0.02%
============================================
Files 133 133
Lines 32725 32733 +8
============================================
+ Hits 23191 23192 +1
- Misses 9534 9541 +7 ☔ View full report in Codecov by Sentry. |
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lgtm. Thanks. |
avagin
approved these changes
Dec 8, 2023
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If ioctl(TIOCSLCKTRMIOS) fails with EPERM it means that a CRIU process lacks of CAP_SYS_ADMIN capability. But we can use ioctl(TIOCGLCKTRMIOS) to read current ->termios_locked value from the kernel and if it's the same as we already have we can skip failing ioctl(TIOCSLCKTRMIOS) safely.
Adrian has recently posted [1] a very good patch to allow ioctl(TIOCSLCKTRMIOS) for processes that have CAP_CHECKPOINT_RESTORE (right now it requires CAP_SYS_ADMIN).
[1] https://lore.kernel.org/all/20231206134340.7093-1-areber@redhat.com/
Suggested-by: Andrei Vagin