Empty extglob patterns hang bash

[John Valko]

Bash hangs when extglobs with no patterns are specified.

Example:

$ echo !()

should print the contents of the current directory, but actually makes bash hang with 100% CPU usage. Also affects other pattern types, e.g. @() and ?(). Non-empty patterns work correctly.

After executing a command containing such a glob, a SIGKILL is required to terminate the process.

Additional info:

$ lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04

$ apt-cache policy bash
bash:
  Installed: 4.3-7ubuntu1.5
  Candidate: 4.3-7ubuntu1.5
  Version table:
 *** 4.3-7ubuntu1.5 0
        500 http://mirrors.linode.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://mirrors.linode.com/ubuntu/ trusty-security/main amd64 Packages
                                                                                        100 /var/lib/dpkg/status
     4.3-6ubuntu1 0
        500 http://mirrors.linode.com/ubuntu/ trusty/main amd64 Packages

[John Valko (jvalko-gmail)]

Also, I built the vanilla bash 4.3 and 4.4 sources and they do not appear to be affected by this bug.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.