This bug was discovered by Matt LeGendre who works at LLNL. He pointed out the problem and corrected my patch to the problem. It seems to exist in quite a range of glibc versions. The problem was discovered in RHEL6's glibc and it still exists in RHEL7 and upstream.

In elf/dl-reloc.c the AUDIT code does a calloc of a library's  DT_PLTRELSZ*sizeof(struct reloc_result) (this is the one we're seeing making ~300MB of allocations).  It's treating the DT_PLTRELSZ as a count of PLTREL entries, but DT_PLTRELSZ is the size in bytes of the PLTREL entries.  So it's doing a much larger memory allocation than necessary.

I looked and the code is the same in RHEL6,7, and upstream glibc.
He suggested a patch like:

diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index d2c6dac..0c85f08 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -280,7 +280,8 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
          }
 
        l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]),
-                                   l->l_info[DT_PLTRELSZ]->d_un.d_val);
+                                   l->l_info[DT_PLTRELSZ]->d_un.d_val /
+                                   (l->l_info[DT_PLTREL]->d_un.d_val == DT_RELA ? sizeof(ElfW(Rela)) : sizeof(ElfW(Rel))));
        if (l->l_reloc_result == NULL)
          {
            errstring = N_("\