500 error when uploading nuget packages.

Summary

When pushing a NuGet package to GitLab, GitLab throws a 500 error

Steps to reproduce

  1. Enable NuGet package repository
  2. Push a package to the repository

Example Project

None, but is easily replicable on a fresh self-managed install of GitLab 12.8.1

What is the current bug behavior?

The package does not get uploaded.

What is the expected correct behavior?

The package gets uploaded to the NuGet registry.

Relevant logs and/or screenshots

UploadedFile::InvalidPathError (insecure path used '/var/opt/gitlab/gitlab-rails/shared/packages/tmp/uploads/package.nupkg646696362'):

lib/uploaded_file.rb:56:in `from_params'
lib/gitlab/middleware/multipart.rb:93:in `open_file'
lib/gitlab/middleware/multipart.rb:47:in `block in with_open_files'
lib/gitlab/middleware/multipart.rb:41:in `each'
lib/gitlab/middleware/multipart.rb:41:in `with_open_files'
lib/gitlab/middleware/multipart.rb:121:in `call'
lib/gitlab/middleware/read_only/controller.rb:53:in `call'
lib/gitlab/middleware/read_only.rb:18:in `call'
lib/gitlab/middleware/basic_health_check.rb:25:in `call'
lib/gitlab/middleware/request_context.rb:23:in `call'
config/initializers/fix_local_cache_middleware.rb:9:in `call'
lib/gitlab/metrics/requests_rack_middleware.rb:49:in `call'
lib/gitlab/middleware/release_env.rb:12:in `call'

Results of GitLab environment info

Expand for output related to GitLab environment info 
System information
System:		Ubuntu 18.04
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.6.5p114
Gem Version:	2.7.10
Bundler Version:1.17.3
Rake Version:	12.3.3
Redis Version:	5.0.7
Git Version:	2.24.1
Sidekiq Version:5.2.7
Go Version:	unknown

GitLab information
Version:	12.8.1-ee
Revision:	13bae744d5c
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	10.12
URL:		https://glhub.dectala.net
HTTP Clone URL:	https://glhub.dectala.net/some-group/some-project.git
SSH Clone URL:	git@glhub.dectala.net:some-group/some-project.git
Elasticsearch:	no
Geo:		no
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers:


GitLab Shell
Version:	11.0.0
Repository storage paths:
  • default: /var/opt/gitlab/git-data/repositories GitLab Shell path: /opt/gitlab/embedded/service/gitlab-shell Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check 
Checking GitLab subtasks ...


Checking GitLab Shell ...


GitLab Shell: ... GitLab Shell version >= 11.0.0 ? ... OK (11.0.0)
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Internal API available: OK
Redis available via internal API: OK
gitlab-shell self-check successful


Checking GitLab Shell ... Finished


Checking Gitaly ...


Gitaly: ... default ... OK


Checking Gitaly ... Finished


Checking Sidekiq ...


Sidekiq: ... Running? ... yes
Number of Sidekiq processes ... 1


Checking Sidekiq ... Finished


Checking Incoming Email ...


Incoming Email: ... Reply by email is disabled in config/gitlab.yml


Checking Incoming Email ... Finished


Checking LDAP ...


LDAP: ... LDAP is disabled in config/gitlab.yml


Checking LDAP ... Finished


Checking GitLab App ...


Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... skipped (no tmp uploads folder yet)
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
2/1 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.5.3 ? ... yes (2.6.5)
Git version >= 2.22.0 ? ... yes (2.24.1)
Git user has default SSH configuration? ... yes
Active users: ... 2
Is authorized keys file accessible? ... yes
Elasticsearch version 5.6 - 6.x? ... skipped (elasticsearch is disabled)


Checking GitLab App ... Finished


Checking GitLab subtasks ... Finished

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)