jailer doesn't ensure correct permissions for /dev inside the jail

[aghecenco]

The jailer creates the /dev, /dev/net and /run folders inside the jail but doesn't ensure that they're accessible for the unprivileged user which firecracker will run under. This can lead to errors when attempting to open devices (dev/kvm and /dev/net/tun), even if the permissions on the devices themselves are correctly set.

firecracker/src/jailer/src/env.rs

Line 180 in 8943f41

fs::create_dir_all(path).map_err(|e| Error::CreateDir(PathBuf::from(path), e))?;