[Bug nptl/21085] New: libthread_db can run into endless loop with corrupt thread list

["matz at suse dot de" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21085

            Bug ID: 21085
           Summary: libthread_db can run into endless loop with corrupt
                    thread list
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: matz at suse dot de
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

Created attachment 9773
  --> https://sourceware.org/bugzilla/attachment.cgi?id=9773&action=edit
tarball with core and libs

This came from a problem in some LTP test, which segfaulted.  Trying to open
the corresponding core with any gdb version hangs in libthread_db in 
iterate_thread_list.  Now it's of course no wonder that if the list is corrupt
that iteration breaks, but perhaps libthread_db can be made a bit more robust
(e.g. counting the loop iterations against an expected number of threads,
or a tortoise-and-hare algorithm to protect against internal cycles).

The attachment contains the exe, the core and the necessary libs to make
gdb not error out with mismatching libs warnings.  Of course for _that_
libthread_db the problem can't be fixed anymore but perhaps for the future.

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