[PATCH] Skip PT_DYNAMIC segment if its p_filesz == 0 [BZ #22101]

[Zack Weinberg]

On Mon, Sep 25, 2017 at 8:33 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> ELF object generated with "objcopy --only-keep-debug" has
>
> Type     Offset  VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> DYNAMIC  0x0+e28 0x0+200e40 0x0+200e40 0x0+    0x0+1a0 RW  0x8
>
> with 0 file size. ld.so should skip such PT_DYNAMIC segments.

Why should ld.so skip such PT_DYNAMIC segments?  It seems like loading
empty segments should be harmless, and ...

> +  void *h = dlopen ("tst-debug1mod1.so", RTLD_LAZY);
> +  if (h != NULL)
> +    {
> +      puts ("shouldn't load tst-debug1mod1.so");

... the implications of this test are scary: I suspect there is code
out there that will break if dlopen starts returning NULL on
completely empty shared objects.

zw