Commit 137df118 authored Oct 16, 2023 by Andrii Nakryiko Committed by Daniel Borkmann Oct 17, 2023

libbpf: Don't assume SHT_GNU_verdef presence for SHT_GNU_versym section



Fix too eager assumption that SHT_GNU_verdef ELF section is going to be
present whenever binary has SHT_GNU_versym section. It seems like either
SHT_GNU_verdef or SHT_GNU_verneed can be used, so failing on missing
SHT_GNU_verdef actually breaks use cases in production.

One specific reported issue, which was used to manually test this fix,
was trying to attach to `readline` function in BASH binary.

Fixes: bb7fa093 ("libbpf: Support symbol versioning for uprobe")
Reported-by: Liam Wisehart <liamwisehart@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Manu Bretelle <chantr4@gmail.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Acked-by: Hengqi Chen <hengqi.chen@gmail.com>
Link: https://lore.kernel.org/bpf/20231016182840.4033346-1-andrii@kernel.org

parent a3c2dd96

tools/lib/bpf/elf.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -141,14 +141,15 @@ static int elf_sym_iter_new(struct elf_sym_iter *iter,
		iter->versyms = elf_getdata(scn, 0);

		scn = elf_find_next_scn_by_type(elf, SHT_GNU_verdef, NULL);
		if (!scn) {
		pr_debug("elf: failed to find verdef ELF sections in '%s'\n", binary_path);
		return -ENOENT;
		}
		if (!gelf_getshdr(scn, &sh))
		if (!scn)
		return 0;

		iter->verdefs = elf_getdata(scn, 0);
		if (!iter->verdefs \|\| !gelf_getshdr(scn, &sh)) {
		pr_warn("elf: failed to get verdef ELF section in '%s'\n", binary_path);
		return -EINVAL;
		}
		iter->verdef_strtabidx = sh.sh_link;
		iter->verdefs = elf_getdata(scn, 0);

		return 0;
		}
		@@ -199,6 +200,9 @@ static const char elf_get_vername(struct elf_sym_iter iter, int ver)
		GElf_Verdef verdef;
		int offset;

		if (!iter->verdefs)
		return NULL;

		offset = 0;
		while (gelf_getverdef(iter->verdefs, offset, &verdef)) {
		if (verdef.vd_ndx != ver) {