Comment 16 for bug 1591868

So I think I've come up with a reliable way to reproduce this by placing a corrupted yaml file in /var/lib/app-info.

Here is the file I placed (notice the extra s at the start):

s---
File: DEP-11
MediaBaseUrl: http://appstream.ubuntu.com/media/main
Origin: ubuntu-xenial-backports-main
Priority: 40
Time: '2016-07-28T18:38:36.877230+00:00'
Version: '0.8'

By running fwupd with that in place, it hangs and pegs at 100% CPU.

The BT of course isn't too surprising where it's hung:

#0 0x00007ffff4249b6f in yaml_parser_parse () from /usr/lib/x86_64-linux-gnu/libyaml-0.so.2
#1 0x00007ffff779e5eb in as_node_yaml_process_layer (parser=parser@entry=0x7fffffffe030, parent=parent@entry=0x555555832c40) at as-yaml.c:225
#2 0x00007ffff779eae0 in as_yaml_from_file (file=file@entry=0x555555830560, cancellable=cancellable@entry=0x0, error=error@entry=0x7fffffffe340) at as-yaml.c:371
#3 0x00007ffff7799481 in as_store_load_yaml_file (error=0x7fffffffe340, cancellable=0x0, file=0x555555830560, store=0x555555795880) at as-store.c:1129
#4 as_store_from_file_internal (store=store@entry=0x555555795880, file=file@entry=0x555555830560, id_prefix=id_prefix@entry=0x7ffff77a29ae "system", cancellable=cancellable@entry=0x0,
    error=error@entry=0x7fffffffe340) at as-store.c:1371
#5 0x00007ffff7799ab7 in as_store_load_app_info_file (error=0x7fffffffe340, cancellable=0x0, path_xml=0x555555798460 "/var/lib/app-info/yaml/yaml.yml", id_prefix=0x7ffff77a29ae "system",
    store=0x555555795880) at as-store.c:2068
#6 as_store_load_app_info (store=store@entry=0x555555795880, id_prefix=id_prefix@entry=0x7ffff77a29ae "system", path=path@entry=0x555555798490 "/var/lib/app-info/yaml",
    flags=flags@entry=AS_STORE_LOAD_FLAG_APP_INFO_SYSTEM, cancellable=cancellable@entry=0x0, error=error@entry=0x7fffffffe4d8) at as-store.c:2118
#7 0x00007ffff779a131 in as_store_search_app_info (store=store@entry=0x555555795880, flags=flags@entry=AS_STORE_LOAD_FLAG_APP_INFO_SYSTEM, id_prefix=id_prefix@entry=0x7ffff77a29ae "system",
    path=path@entry=0x555555798430 "/var/lib/app-info", cancellable=cancellable@entry=0x0, error=error@entry=0x7fffffffe4d8) at as-store.c:2333
#8 0x00007ffff779abe4 in as_store_search_per_system (error=<optimized out>, cancellable=0x0, flags=<optimized out>, store=<optimized out>) at as-store.c:2535
#9 as_store_load (store=<optimized out>, flags=<optimized out>, cancellable=0x0, error=<optimized out>) at as-store.c:2683
#10 0x000055555555d9c7 in main ()