From: Andrii Nakryiko <andrii@kernel.org>
Date: Tue, 23 Nov 2021 16:23:16 -0800
Subject: libbpf: Don't call libc APIs with NULL pointers
Patch-mainline: v5.17-rc1
Git-commit: 2a6a9bf26170b4e156c18706cd230934ebd2f95f
References: jsc#PED-1368

Sanitizer complains about qsort(), bsearch(), and memcpy() being called
with NULL pointer. This can only happen when the associated number of
elements is zero, so no harm should be done. But still prevent this from
happening to keep sanitizer runs clean from extra noise.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-5-andrii@kernel.org
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/lib/bpf/libbpf.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3369,7 +3369,8 @@ static int bpf_object__elf_collect(struc
 
 	/* sort BPF programs by section name and in-section instruction offset
 	 * for faster search */
-	qsort(obj->programs, obj->nr_programs, sizeof(*obj->programs), cmp_progs);
+	if (obj->nr_programs)
+		qsort(obj->programs, obj->nr_programs, sizeof(*obj->programs), cmp_progs);
 
 	return bpf_object__init_btf(obj, btf_data, btf_ext_data);
 }
@@ -5823,6 +5824,8 @@ static int cmp_relo_by_insn_idx(const vo
 
 static struct reloc_desc *find_prog_insn_relo(const struct bpf_program *prog, size_t insn_idx)
 {
+	if (!prog->nr_reloc)
+		return NULL;
 	return bsearch(&insn_idx, prog->reloc_desc, prog->nr_reloc,
 		       sizeof(*prog->reloc_desc), cmp_relo_by_insn_idx);
 }
@@ -5838,8 +5841,9 @@ static int append_subprog_relos(struct b
 	relos = libbpf_reallocarray(main_prog->reloc_desc, new_cnt, sizeof(*relos));
 	if (!relos)
 		return -ENOMEM;
-	memcpy(relos + main_prog->nr_reloc, subprog->reloc_desc,
-	       sizeof(*relos) * subprog->nr_reloc);
+	if (subprog->nr_reloc)
+		memcpy(relos + main_prog->nr_reloc, subprog->reloc_desc,
+		       sizeof(*relos) * subprog->nr_reloc);
 
 	for (i = main_prog->nr_reloc; i < new_cnt; i++)
 		relos[i].insn_idx += subprog->sub_insn_off;