Adding a new section to an ELF file aborts with Assertion `shdr != NULL'

Alexander Egorenkov egorenar@posteo.net
Sat Sep 4 09:13:33 GMT 2021


Hi all,

Alexander Egorenkov <egorenar-dev@posteo.net> writes:

> Hi all,
>
> i'm facing an issue with libelf when i try to add a new section to an
> ELF file.
>
> How to reproduce the issue:
> 1. Create a simple ELF file with libelf containing only 2 sections, NULL and
> a string table
> 2. Close ELF file
> 3. Reopen the new ELF file in RW mode with libelf
> 4. Add new section with elf_newscn()
> 5. Update ELF with elf_update()
> 6. Assertion appears
>
> The weird thing is that if i add only a new program segment then
> everything goes well. But as soon as i add a new section, it fails.
>
> Error message:
>
> test: elf32_updatenull.c:214: __elf64_updatenull_wrlock: Assertion `shdr
> != NULL' failed.
>
> Any hint what i'm doing wrong ? 
>

One workaround i found is this:

	scn = elf_getscn(elf, 0);
	shdr = elf64_getshdr(scn);

It seems that __elf64_updatenull_wrlock() tries to access the section
header of the NULL section.

Regards
Alex




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