[Bug 687594] Re: tar crashes with SIGSEGV when used with --listed-incremental option and including the root directory

[Marcel Stimberg]

Given the positive review of the patch, the bug being a regression and
its impact on typical backup scripts -- would someone be willing to
upload it to proposed?

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https://bugs.launchpad.net/bugs/687594

Title:
  tar crashes with SIGSEGV when used with --listed-incremental option  and including the root directory

Status in “tar” package in Ubuntu:
  Fix Released
Status in “tar” package in Debian:
  Unknown

Bug description:
  Binary package hint: tar

I have a backup script which is doing incremental backups on NFS share. I am using an -g (--listed-incremental) option for that purpose. If the snapshot file does not exists (which means tar is doing full backups) everything works flawlessly. The problem occur whenever incremental backup has to be taken. Tar crashes immediately with Segmentation Fault error. I have tried to isolate NFS issues and copied the snapshot file to local storage and instructed tar to put the archive to local drive as well. The result was exactly the same. The problem occurs whenever the root directory "/" is included in the backup.

TEST CASE:
  $ tar cpf /tmp/test.tar -g /tmp/snap / --exclude="*"
  $ tar cpf /tmp/test.tar -g /tmp/snap / --exclude="*"
  Segmentation fault

After applying the fix in the linked branch, tar no longer segfaults. The patch is taken from this upstream commit:
http://git.savannah.gnu.org/cgit/tar.git/commit/?id=e21d54e8cd3d8026ad56f90cc6bde831106c2cb9

The bug is a regression introduced in Maverick.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: tar 1.23-2
ProcVersionSignature: Ubuntu 2.6.35-22.35-server 2.6.35.4
Uname: Linux 2.6.35-22-server x86_64
Architecture: amd64
Date: Thu Dec  9 00:12:35 2010
InstallationMedia: Ubuntu-Server 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: tar

== Regression details ==
Discovered in version: 1.23-2
Last known good version: 1.22-2ubuntu1