[Bug dynamic-link/24476] __libc_freeres triggers bad free in libdl if dlerror was not used

["mark at klomp dot org" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=24476

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Mark Wielaard <mark at klomp dot org> ---
commit 11b451c8868d8a2b0edc5dfd44fc58d9ee538be0
Author: Mark Wielaard <mark@klomp.org>
Date:   Wed May 15 17:14:01 2019 +0200

    dlfcn: Guard __dlerror_main_freeres with __libc_once_get (once) [BZ# 24476]

    dlerror.c (__dlerror_main_freeres) will try to free resources which only
    have been initialized when init () has been called. That function is
    called when resources are needed using __libc_once (once, init) where
    once is a __libc_once_define (static, once) in the dlerror.c file.
    Trying to free those resources if init () hasn't been called will
    produce errors under valgrind memcheck. So guard the freeing of those
    resources using __libc_once_get (once) and make sure we have a valid
    key. Also add a similar guard to __dlerror ().

        * dlfcn/dlerror.c (__dlerror_main_freeres): Guard using
        __libc_once_get (once) and static_bug == NULL.
        (__dlerror): Check we have a valid key, set result to static_buf
        otherwise.

    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

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