rootless: fix SIGSEGV, Make LISTEN_FDNAMES optional

[flouthoc]

Reproduce SIGSEGV

#!/bin/bash
export LISTEN_PID=$$
export LISTEN_FDS=1
exec podman run --rm registry.fedoraproject.org/fedora:34 /bin/true

[NO TESTS NEEDED]: I think test for this would be a basic run with LISTEN_PID and LISTEN_FDS set and since no new feature or significant behavior change is being added so putting more tests might not be necessary. But sure let me know if having new tests here makes sense.
Closes: #10435

[giuseppe]

LGTM

[openshift-ci]

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[rhatdan]

@giuseppe shouldn't we be saving the ones that are set. LISTEN_FDNAMES is optional, so we should just handle that case.

[giuseppe]

@giuseppe shouldn't we be saving the ones that are set. LISTEN_FDNAMES is optional, so we should just handle that case.

ah right, yes in that case we need to handle LISTEN_FDNAMES to be null.

@flouthoc could you please fix it in the patch?

[flouthoc]

@rhatdan @giuseppe Sure makes sense, we could make this optional instead.

[flouthoc]

@giuseppe @rhatdan I have made requested changes. Could you please take a look ? I think one failing check is a flake.

[rhatdan]

LGTM

[eriksjolund]

Thanks @flouthoc for fixing the issue!

It seems there is no reference in the commit message to the Github issue.

https://github.com/containers/podman/blob/master/CONTRIBUTING.md
PRs that fix issues should include a reference like Closes #XXXX in the commit message so that GitHub will automatically close the referenced issue when the PR is merged.

Another thing, regarding:
"Ref: #10435"
in the comment.
Ref does not seem to be one of the keywords that links a pull request to an issue:
https://docs.github.com/en/issues/tracking-your-work-with-issues/creating-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword

[flouthoc]

@eriksjolund thanks for pointing this out 😄 .Adding it now Closes: #10435

[eriksjolund]

Thanks @flouthoc Could you also add

Closes #10435

in the commit message? (The information will then be preserved in the commit log. Another advantage is that it will help GitHub provide a convenient hyperlink to the issue when displaying the Git commit on their website)

Running git log I see that there are also other styles that works as well, for instance

Closes: https://github.com/containers/podman/issues/10435

[flouthoc]

@eriksjolund Done. Let me know if anything else needs to be done. 🙂

[eriksjolund]

@flouthoc Thanks, to me it looks fine. I now see the GitHub hyperlink in flouthoc@2addc0f

[rhatdan]

/lgtm