[PATCH bpf-next 0/2] Fix double-free when linker processes empty sections

[Eduard Zingerman <eddyz87@gmail.com>]

Fixes double-free error in linker.c:bpf_linker__free() caused by
realloc(..., 0) call in linker.c:extend_sec() (such a call "frees"
memory every second time :). The error is triggered when object files
with empty sections of the same name are processed by linker.

- The first patch extends progs/linked_funcs[12].c to trigger the
  error upon tests compilation;
- The second patch contains detailed description of the error, fix and
  appropriate attributions.

Eduard Zingerman (2):
  selftests/bpf: Test if bpftool linker handles empty sections
  libbpf: Fix double-free when linker processes empty sections

 tools/lib/bpf/linker.c                            | 14 +++++++++++++-
 tools/testing/selftests/bpf/progs/linked_funcs1.c |  3 +++
 tools/testing/selftests/bpf/progs/linked_funcs2.c |  3 +++
 3 files changed, 19 insertions(+), 1 deletion(-)

-- 
2.40.0