There is a problem with the default location used by runsc when the --root flag is not set

[unknowndevQwQ]

Description

The --root flag is not specified by default when running runsc with podman, and the default location in https://github.com/google/gvisor/blob/master/runsc/config/flags.go#L126-L132 is found to be /var/run/runsc, but it actually uses the runsc folder under the relative path (the folder specified by the path of the --bundle flag when checked with sysdig)
This problem still exists in the latest version (20211101)

As a side note, it is now recommended to use /run instead of /var/run

Steps to reproduce

sudo podman --cgroup-manager cgroupfs --runtime runsc --runtime-flag debug --runtime-flag debug-log=/tmp/runsc.log run --rm hello-world; grep RootDir /tmp/runsc.log

output:

I1110 1xxx   47873 main.go:226]              RootDir: runsc
I1110 1xxx   47880 main.go:226]              RootDir: runsc

runsc version

runsc version release-20211011.0

runsc debug logs (if available)

https://fars.ee/C6cG

[fvoznika]

Hmm, this can only happen if XDG_RUNTIME_DIR is set. Can you check if env | grep XDG_RUNTIME_DIR is set? Or is Podman setting it before calling the runtime by any chance?

$ ./runsc --debug --alsologtostderr 2>&1 | grep RootDir
I1111 10:21:48.247946  2448312 main.go:226]             RootDir: /var/run/runsc

$ XDG_RUNTIME_DIR="" ./runsc --debug --alsologtostderr 2>&1 | grep RootDir
I1111 10:22:01.988431  2448423 main.go:226]             RootDir: runsc

[unknowndevQwQ]

Hmm, this can only happen if XDG_RUNTIME_DIR is set. Can you check if env | grep XDG_RUNTIME_DIR is set? Or is Podman setting it before calling the runtime by any chance?

$ ./runsc --debug --alsologtostderr 2>&1 | grep RootDir
I1111 10:21:48.247946  2448312 main.go:226]             RootDir: /var/run/runsc

$ XDG_RUNTIME_DIR="" ./runsc --debug --alsologtostderr 2>&1 | grep RootDir
I1111 10:22:01.988431  2448423 main.go:226]             RootDir: runsc

XDG_RUNTIME_DIR environment variable with a null value in the environment variable passed to runsc by podman found by frun

/tmp/frun.out: https://fars.ee/q6ii

[ianlewis]

I suppose we should ignore it if the value is empty. Currently we use the bool returned by LookupEnv when we probably should just do Getenv and check if it's an empty string.

Containerd checks for empty values for example:
https://github.com/containerd/containerd/search?q=XDG_RUNTIME_DIR