[PATCH] Avoid concurrency problem in ldconfig (bug 23973)

[Florian Weimer]

* Andreas Schwab:

> On Apr 18 2019, Florian Weimer <fweimer@redhat.com> wrote:
>
>> * Andreas Schwab:
>>
>>> Use a unique name for the temporary file when updating the ld.so cache, so
>>> that two concurrent runs of ldconfig don't write to the same file.
>>>
>>> 	* elf/cache.c (save_cache): Use unique temporary name.
>>> 	(save_aux_cache): Likewise.
>>
>> The downside of this change is that if ldconfig is interrupted, the
>> temporary file never goes away.
>>
>> Ideally, we would use O_TMPFILE if supported by the (file) system, but
>> that can get quite involved.
>
> That shortens the window, but won't close it, since we need a name to
> pass to rename in any case.

The difference is that with a fixed name, the next ldconfig run will use
the same name and rename, cleaning up.  With a random, unique name, that
automatic cleanup is gone.

Thanks,
Florian