Limit CI job group_name regexp

Merge branch 'security-improve-ci-job-group-name-regexp-14-10' into '14-10-stable-ee'

See merge request gitlab-org/security/gitlab!2382

Changelog: security

app/models/commit_status.rb

@@ -229,7 +229,13 @@ class CommitStatus < Ci::ApplicationRecord
   end
   def group_name
-    name.to_s.sub(%r{([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z}, '').strip
+    # [\b\s:] -> whitespace or column
+    # (\[.*\])|(\d+[\s:\/\\]+\d+) -> variables/matrix or parallel-jobs numbers
+    # {1,3} -> number of times that matches the variables/matrix or parallel-jobs numbers
+    #          we limit this to 3 because of possible abuse
+    regex = %r{([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+))){1,3}\s*\z}
+
+    name.to_s.sub(regex, '').strip
   end
   def failed_but_allowed?

doc/ci/jobs/index.md

@@ -167,7 +167,7 @@ The jobs are ordered by comparing the numbers from left to right. You
 usually want the first number to be the index and the second number to be the total.
 [This regular expression](https://gitlab.com/gitlab-org/gitlab/-/blob/2f3dc314f42dbd79813e6251792853bc231e69dd/app/models/commit_status.rb#L99)
-evaluates the job names: `([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z`.
+evaluates the job names: `([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+))){1,3}\s*\z`.
 One or more `: [...]`, `X Y`, `X/Y`, or `X\Y` sequences are removed from the **end**
 of job names only. Matching substrings found at the beginning or in the middle of
 job names are not removed.

spec/models/commit_status_spec.rb

@@ -618,6 +618,7 @@ RSpec.describe CommitStatus do
       'rspec:windows 10000 20000'                           | 'rspec:windows'
       'rspec:windows 0 : / 1'                               | 'rspec:windows'
       'rspec:windows 0 : / 1 name'                          | 'rspec:windows 0 : / 1 name'
+      'rspec [inception: [something, other thing], value]'  | 'rspec'
       '0 1 name ruby'                                       | '0 1 name ruby'
       '0 :/ 1 name ruby'                                    | '0 :/ 1 name ruby'
       'rspec: [aws]'                                        | 'rspec'