C/R memfd file permissions

[codecov-commenter]

Codecov Report

Patch coverage: 71.42% and project coverage change: +0.27% :tada:

Comparison is base (988a5f4) 70.36% compared to head (52d2376) 70.64%. Report is 1 commits behind head on criu-dev.

:exclamation: Current head 52d2376 differs from pull request most recent head c05dbc5. Consider uploading reports for the commit c05dbc5 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## criu-dev #2230 +/- ## ============================================ + Coverage 70.36% 70.64% +0.27% ============================================ Files 134 133 -1 Lines 34039 33318 -721 ============================================ - Hits 23952 23536 -416 + Misses 10087 9782 -305 ``` | [Files Changed](https://app.codecov.io/gh/checkpoint-restore/criu/pull/2230?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [criu/memfd.c](https://app.codecov.io/gh/checkpoint-restore/criu/pull/2230?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y3JpdS9tZW1mZC5j) | `81.77% <71.42%> (-0.05%)` | :arrow_down: | ... and [14 files with indirect coverage changes](https://app.codecov.io/gh/checkpoint-restore/criu/pull/2230/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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[avagin]

pls write in the commit message when memfd file permissions are matter. Commit messages can't be empty except very trivial patches.

[osctobe]

Done.