[Bug 1790671] [NEW] /usr/lib/packagekit/packagekitd:11:std::__cxx11::basic_string:AptIntf::providesCodec:backend_what_provides_thread:pk_backend_job_thread_setup:g_thread_proxy

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Rik Mills (rikmills):

[Impact]
pkcon what-provides and other tools querying codecs do not work, they crash (unless you happen to be lucky with your apt cache). Also, cancalled transactions crash as well, even if you're lucky with your apt cache, as the "matcher" object is deleted twice.

There are two reasons: A duplicate delete statement in providesCodec
entered when cancelling the lookup, and a invalid pointer dereference in
there.

[Test case]
The daemon should not crash as below, but should print a useful message.

$ lxc launch -e ubuntu:bionic bbb
$ lxc exec bbb apt update
$ lxc exec bbb -- apt  -y  install packagekit
$ lxc exec bbb pkcon what-provides  "gstreamer1.0(decoder-audio/ac3)"
[...] The daemon crashed mid-transaction!

(empty lxd container seems to be able to reproduce easily)

This only tests the pointer dereference, I don't have a test for the
duplicate. But the code is obviously correct:

 for ... [
   if (m_cancel) {
     // here used to be "delete matcher" - that's deleted
     break;
   }
 }
 delete matcher;

That is, matcher is always deleted once now, and was always deleted
twice when cancelling before.

[Regression potential]
I don't think it's possible to have a regression here, given the nature of the fix, but if there were one, we'd see different behavior in codec lookup.

For the duplicate delete on cancelled transactions, you'd be looking at
memory leaks if there were a regression.

[Other info]
The Ubuntu Error Tracker has been receiving reports about a problem regarding packagekit.  This problem was most recently seen with package version 1.1.10-1ubuntu2, the problem page at https://errors.ubuntu.com/problem/46649a8a55e07e74b9d522c9bc9d71a74905ccc2 contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

** Affects: packagekit (Ubuntu)
     Importance: High
     Assignee: Julian Andres Klode (juliank)
         Status: Fix Released

** Affects: packagekit (Ubuntu Bionic)
     Importance: Undecided
         Status: Fix Committed


** Tags: artful bionic cosmic kylin-17.10 verification-done verification-done-bionic
-- 
/usr/lib/packagekit/packagekitd:11:std::__cxx11::basic_string:AptIntf::providesCodec:backend_what_provides_thread:pk_backend_job_thread_setup:g_thread_proxy
https://bugs.launchpad.net/bugs/1790671
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