misc/162016: BSDPAN::ExtUtils::Packlist->get_dir_list can go into an infinite loop

[Michael G Schwern]

>Number:         162016
>Category:       misc
>Synopsis:       BSDPAN::ExtUtils::Packlist->get_dir_list can go into an infinite loop
>Confidential:   no
>Severity:       non-critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Oct 25 23:00:19 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Michael G Schwern
>Release:        8.2
>Organization:
>Environment:
8.2-RELEASE i386 (I can't cut & paste from my virtual machine)
>Description:
See https://rt.cpan.org/Ticket/Display.html?id=70232#txn-991950 for the upstream report.

BSDPAN::ExtUtils::Packlist can be put into an infinite loop if write() is given a packlist like "../.packlist".  This happens in the ExtUtils-MakeMaker tests, specifically t/INSTALL_BASE.t, and was causing hangs.

I have worked around this in MakeMaker's tests by having them set one of the magic environment variables it recognizes to disable BSDPAN registration.  It's a bit distressing that test modules were being registered.  Perhaps BDSPAN should check that the module in question is being installed into an official location before registering?  I don't know how the BSDPAN stuff works.
>How-To-Repeat:
cd Some-CPAN-Module (ExtUtils-MakeMaker works)
perl Makefile.PL (to generate a Makefile)

Then run the following Perl program.

    use ExtUtils::Packlist;
    my $packlist = ExtUtils::Packlist->new;
    $packlist->{"Bar.pm"} = 1;
    $packlist->write("../.packlist");

It will enter an infinite loop.
>Fix:
get_dir_list() is the problem.  It's written in an unsafe fashion.  Instead of hacking off bits of the filepath with a regex and breaking out of an infinite loop, it is safer and simpler to pull the filepath apart into a list with File::Spec->splitpath and iterate through it.

>Release-Note:
>Audit-Trail:
>Unformatted: