cgroup-info: check if user.slice is valid before accessing value

[flouthoc]

Prevent hitting panic: runtime error: index out of range [1] with length 1
while performingpodman info and we get unexpected values for user.slice.

[mheon]

Tentative LGTM, but I would really like to know what's going on such that the cgroup path is invalid

[flouthoc]

@mheon For this case If user.slice is invalid falls back to getting subsystem details from parent.

[zhangguanzhang]

I think should check it equal to 2 rather than this change

[flouthoc]

@zhangguanzhang that should also do the trick.I'll make the change

[vrothberg]

LGTM
@giuseppe PTAL

[giuseppe]

LGTM

[openshift-ci]

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[vrothberg]

/lgtm

[giuseppe]

given the comment: #11461 (comment)

I am not sure this is the right fix.

Should we skip the line and try with the next one (where the cgroup v2 mount is)?

EDIT: nevermind, it should work as it is

[flouthoc]

Just to specify if someone else revisits the thread, loop will start processing another line here if first entry is invalid https://github.com/containers/podman/blob/main/pkg/cgroups/cgroups.go#L231