https://sourceware.org/bugzilla/show_bug.cgi?id=34798
Bug ID: 34798
Summary: GNU ld forms NULL + 0 for an empty AVR
output-relocation array
Product: binutils
Version: 2.47
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: basavesh.shivakumar at wsu dot edu
Target Milestone: ---
Created attachment 17118
--> https://sourceware.org/bugzilla/attachment.cgi?id=17118&action=edit
reproducer
I'm reporting this bug on behalf of my team: Ananta Srikar Puranam, Emily West,
Dr. Swarn Priya, Dr. Peng Gao and Dr. Basavesh Ammanaghatta Shivakumar.
Summary
=======
An AVR relocatable or --emit-relocs link creates a .trampolines output section
with SEC_RELOC and zero relocations, then elf_link_input_bfd evaluates NULL + 0
at bfd/elflink.c:12011 in the tested current snapshot (12013 after nearby
changes). An adjacent earlier expression at line 11826/11828 is covered by the
separate zero-entry-relocation report; a recoverable UBSan build continues
through that report and diagnoses this second site. Ordinary builds complete
because the following loop has zero iterations.
Reproduction
============
1. Download and extract
`bfd-empty-table-null-pointer-arithmetic-avr-elf-reproducer.tar.gz`.
2. Run the following command with an ld.bfd or all-target `ld-new` binary that
supports the emulation used by the reproducer:
LD=/path/to/ld-new sh repro.sh
The archive contains the fixed input files, independent controls, helper
scripts needed by `repro.sh`, and their checksums. The script uses a temporary
directory and does not modify the source tree.
Observed result
===============
An AVR relocatable or --emit-relocs link creates a .trampolines output section
with SEC_RELOC and zero relocations, then elf_link_input_bfd evaluates NULL + 0
at bfd/elflink.c:12011 in the tested current snapshot (12013 after nearby
changes). An adjacent earlier expression at line 11826/11828 is covered by the
separate zero-entry-relocation report; a recoverable UBSan build continues
through that report and diagnoses this second site. Ordinary builds complete
because the following loop has zero iterations.
Expected result
===============
GNU ld should either produce the correct output or reject the input with a
normal diagnostic. It should not crash, hang, execute undefined behavior, read
outside an input-derived allocation, or produce the described malformed
output.
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