Infinite loop on gemset create if the user does not have write permissions

[DanielRussell]

Description

When a user attempts to create a new gemset, but does not have write permissions in the gem directory, rvm goes into an infinite loop.

Steps to reproduce

1. Perform a Multi-User
2. Ensure a user is not a member of the rvm group
3. Run /usr/local/rvm/bin/rvm ruby-2.4.1 gemset create my-gemset

NOTE: I'm running rvm directly like this because it's part of a CI job; easier to run directly than to source into the environment.

Expected behavior

I would expect rvm to return an error.

Actual behavior

Infinite loop / fork bomb which required a system reboot.

$ groups
users docker
$ ls -dl /usr/local/rvm/gems/ruby-2.4.1
drwxrwsr-x 6 root rvm 4096 May  5 15:23 /usr/local/rvm/gems/ruby-2.4.1
$ /usr/local/rvm/bin/rvm ruby-2.4.1 gemset create my-gemset
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
ruby-2.4.1 - #gemset created /usr/local/rvm/gems/ruby-2.4.1@my-gemset
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
ruby-2.4.1 - #gemset created /usr/local/rvm/gems/ruby-2.4.1@my-gemset
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
mkdir: cannot create directory ‘/usr/local/rvm/gems/ruby-2.4.1@my-gemset’: Permission denied
...

Environment info

$ rvm info

ruby-2.2.3:

  system:
    uname:        "Linux my-hostname 4.9.32-15.41.amzn1.x86_64 #1 SMP Thu Jun 22 06:20:54 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux"
    name:         "Amazon"
    version:      "2017.03"
    architecture: "x86_64"
    bash:         "/bin/bash => GNU bash, version 4.2.46(1)-release (x86_64-redhat-linux-gnu)"
    zsh:          " => not installed"
    remote path:  "amazon/2017.03/x86_64"

  rvm:
    version:      "rvm 1.29.2 (latest) by Michal Papis, Piotr Kuczynski, Wayne E. Seguin [https://rvm.io/]"
    updated:      "11 minutes 46 seconds ago"
    path:         "/usr/local/rvm"
    autolibs:     "[4] Allow RVM to use package manager if found, install missing dependencies, install package manager (only OS X)."

  ruby:
    interpreter:  "ruby"
    version:      "2.2.3p173"
    date:         "2015-08-18"
    platform:     "x86_64-linux"
    patchlevel:   "2015-08-18 revision 51636"
    full_version: "ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]"

  homes:
    gem:          "/usr/local/rvm/gems/ruby-2.2.3"
    ruby:         "/usr/local/rvm/rubies/ruby-2.2.3"

  binaries:
    ruby:         "/usr/local/rvm/rubies/ruby-2.2.3/bin/ruby"
    irb:          "/usr/local/rvm/rubies/ruby-2.2.3/bin/irb"
    gem:          "/usr/local/rvm/rubies/ruby-2.2.3/bin/gem"
    rake:         "/usr/local/rvm/rubies/ruby-2.2.3/bin/rake"

  environment:
    PATH:         "/usr/local/rvm/gems/ruby-2.2.3/bin:/usr/local/rvm/gems/ruby-2.2.3@global/bin:/usr/local/rvm/rubies/ruby-2.2.3/bin:/usr/local/src/nvm/versions/node/v4.2.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/usr/local/go/bin:/usr/local/go-global/bin:/opt/aws/bin:/usr/local/rvm/bin:/home/dpr/bin"
    GEM_HOME:     "/usr/local/rvm/gems/ruby-2.2.3"
    GEM_PATH:     "/usr/local/rvm/gems/ruby-2.2.3:/usr/local/rvm/gems/ruby-2.2.3@global"
    MY_RUBY_HOME: "/usr/local/rvm/rubies/ruby-2.2.3"
    IRBRC:        "/usr/local/rvm/rubies/ruby-2.2.3/.irbrc"
    RUBYOPT:      ""
    gemset:       ""