[Bug dynamic-link/14681] _dl_get_origin leaks memory via executable link map.

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https://sourceware.org/bugzilla/show_bug.cgi?id=14681

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=93930ea9351c0c4a239e3dcb83f1398cce4e4d43

commit 93930ea9351c0c4a239e3dcb83f1398cce4e4d43
Author: Carlos O'Donell <carlos@redhat.com>
Date:   Tue Dec 12 20:35:05 2017 -0800

    Fix tst-leaks1 (bug 14681)

    The test tst-leaks1 exercises calling dlopen with a $ORIGIN DST.

    This results in a theoretical leak e.g.

    Memory not freed:
    -----------------
               Address     Size     Caller
    0x0000000001d766c0     0x21  at 0x7fb1bd8bf4ab

    Or as seen via valgrind:

    ==27582== 33 bytes in 1 blocks are still reachable in loss record 1 of 1
    ==27582==    at 0x4C2CB6B: malloc (vg_replace_malloc.c:299)
    ==27582==    by 0x40124AA: _dl_get_origin (dl-origin.c:50)
    ==27582==    by 0x4007DB9: expand_dynamic_string_token (dl-load.c:382)
    ==27582==    by 0x400899C: _dl_map_object (dl-load.c:2160)
    ==27582==    by 0x4013020: dl_open_worker (dl-open.c:224)
    ==27582==    by 0x5166F9B: _dl_catch_exception (dl-error-skeleton.c:198)
    ==27582==    by 0x4012BD9: _dl_open (dl-open.c:594)
    ==27582==    by 0x4E39EF5: dlopen_doit (dlopen.c:66)
    ==27582==    by 0x5166F9B: _dl_catch_exception (dl-error-skeleton.c:198)
    ==27582==    by 0x516700E: _dl_catch_error (dl-error-skeleton.c:217)
    ==27582==    by 0x4E3A514: _dlerror_run (dlerror.c:162)
    ==27582==    by 0x4E39F70: dlopen@@GLIBC_2.2.5 (dlopen.c:87)

    There is no real leak.

    The calling link map (the executable's link map) has it's l_origin
    expanded for future use as part of _dl_get_origin, and that results
    in the main executable link map having a N-byte allocation for
    l->l_origin that is never freed since the executable's link map is
    just a part of the process.

    To take this into account we do one dlopen with $ORIGIN before
    calling mtrace to force the initialization of the executable link
    map.

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

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog        |    6 ++++++
 elf/tst-leaks1.c |   21 ++++++++++++++++++---
 2 files changed, 24 insertions(+), 3 deletions(-)

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