A map=NULL seems to be missing.
efree() does nothing more than free().

The lines in if (map == ..) won't be executed ever when using Zend memory manager, because it bails out immediately on OOM error, so the only way to get them executed is to disable Zend MM and go with system MM.

man free says: 
If ptr is NULL, no operation is performed.

apprentice_unmap():
    if (map == NULL)
        return;

So.. where is the problem here?

'map' is not NULL. efree(map) doesn't set map=NULL;.

That's correct, efree() doesn't modify the pointer.
But it's already NULL at the time efree() is called, take a look at the if condition:

    if ((map = CAST(struct magic_map *, ecalloc(1, sizeof(*map)))) == NULL) {
        file_oomem(ms, sizeof(*map));
        efree(map);
        goto error;
    }

Ahh, I see!

Well, then, this code:

2611                efree(map);
2612                goto error;

should just be replaced with 
return NULL;
since 'dbname', and 'stream' are not used at that stage.

Thanks,

This is a file from fileinfo library, so it may make sense to report the issue here; http://bugs.gw.com/my_view_page.php

In this particular case return NULL may indeed be faster, but I don't see any security issue or PHP-related bug here.

@stas 

as it is a fileinfo issue and should also reported there, we do bundle it, patched. So it affects PHP more directly too. We should apply the fix.

Looks like it's an issue in the PHP patch, the latest libmagic looks fine https://github.com/file/file/blob/master/src/apprentice.c#L1283 . Despite it's only an issue with disabled ZMM, worth fixing.

Thanks.