[Bug 1579712] Re: Refresh hangs due to strdup on non-NULL terminated string

[John Wang]

@ximion: I missed that. After upgrading libappstream3 from -proposed,
everything works fine. Thanks.

The reason I warned against removing the binary is because it's a bad
practice in general, even though in this particular problem scenario the
removed binary gets restored when its package is upgraded. Package-
managed files should only be removed as a last resort when there isn't a
better/safer workaround that won't potentially leave any part of the
system in a broken or inconsistent state at any point in time. In this
case, a safe workaround does exist, which is to disable appstream's apt
config in the canonically-prescribed manner: appending ".disabled" to
the config's filename.

So the complete procedure to fix this safely would be:

$ sudo mv /etc/apt/apt.conf.d/50appstream /etc/apt/apt.conf.d/50appstream.disabled
$ cd /tmp && mkdir asfix
$ cd asfix
$ wget https://launchpad.net/ubuntu/+archive/primary/+files/appstream_0.9.4-1ubuntu1_amd64.deb
$ wget https://launchpad.net/ubuntu/+archive/primary/+files/libappstream3_0.9.4-1ubuntu1_amd64.deb
$ sudo dpkg -i *.deb
$ sudo mv /etc/apt/apt.conf.d/50appstream.disabled /etc/apt/apt.conf.d/50appstream

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https://bugs.launchpad.net/bugs/1579712

Title:
  Refresh hangs due to strdup on non-NULL terminated string

Status in appstream package in Ubuntu:
  Fix Released
Status in appstream source package in Xenial:
  Fix Committed

Bug description:
  [Impact]

   * The cache refresh is blocked on a strdup on a non-NULL-terminated string in some very rare occasions (very rare because this bug is present for almost 3y without a single report).
   * Fixing this bug resolves the issue for people who might experience it.
   * See https://github.com/ximion/appstream/issues/35 for details.

  [Test Case 1]

   * Run `sudo appstreamcli refresh --force`
   * The AppStream cache should be updated, no change in behavior should be seen.

  [Test Case 2]

   * In case you were experiencing the almost-infinite hang when running
  `sudo appstreamcli refresh --force`, this issue should be fixed with
  the SRU.

  [Regression Potential]

   * Very low, since this only fixes the decompression code. There
  should be no sideeffects of that (given that the patch itself doesn't
  break anything, which it shouldn't, since it has been tested upstream
  for a while)

  [Other Info]

   * This fix has been applied upstream: https://github.com/ximion/appstream/commit/f33c520c37e2ba51d92402220250b8d501a2bf43
   * A smaller version of the patch (one-liner) is available, at the expense of not having reduced memory usage: https://github.com/ximion/appstream/commit/378941787d3584b3eb31a6ebe40e0aacc10e180a

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