Document setgroups call caused by std::os::unix::process::CommandExt.uid

[Elliot-Roberts]

Fixes #39186
It's a small change but this is my first time contributing to open source so any feedback is very appreciated.

I also have some questions:
I documented that the setgroup call only happens when the parent is root. But this is potentially not the desired behavior, as described in #88716.
What more needs to happen decision-wise for that? Does #88716 remaining open mean that it is an approved and wanted change? I could fix that issue in this PR too if that would be ok.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Mark-Simulacrum (or someone else) soon.

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[Mark-Simulacrum]

r? @joshtriplett perhaps? This likely wants FCP, but I'm also not sure we want to make the guarantee this specific.

[joshtriplett]

I do think this warrants an FCP.

I think if we're going to have behavior this specific (and potentially unexpected), we should document it.

@rfcbot merge

[rfcbot]

Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se
• @yaahc

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

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[Elliot-Roberts]

Is the current behavior the one we want to keep? The specifics I wrote conflict with what #88716 wants.
Specifically, I say "This will also trigger a call to setgroups(0, NULL) in the child process if the parent is root ..."
Whereas implementing the change requested in #88716 would mean the call is triggered for any process that has the CAP_SETGID capability.

[Amanieu]

I agree that would should document this, however we should first resolve #88716 to decide the actual behavior we want to stabilize.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[JohnCSimon]

triage:
looks like #88716 is still waiting on resolution

[Elliot-Roberts]

Closing in favor of #95982