libbpf: Detect corrupted ELF symbols section

mainline inclusion
from mainline-5.17-rc1
commit 83390787
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=833907876be55205d0ec153dcd819c014404ee16

-------------------------------------------------

Prevent divide-by-zero if ELF is corrupted and has zero sh_entsize.
Reported by oss-fuzz project.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211103173213.1376990-2-andrii@kernel.org
(cherry picked from commit 83390787)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/libbpf.c

@@ -3513,7 +3513,7 @@ static int bpf_object__collect_externs(struct bpf_object *obj)
 
 	scn = elf_sec_by_idx(obj, obj->efile.symbols_shndx);
 	sh = elf_sec_hdr(obj, scn);
-	if (!sh)
+	if (!sh || sh->sh_entsize != sizeof(Elf64_Sym))
 		return -LIBBPF_ERRNO__FORMAT;
 
 	dummy_var_btf_id = add_dummy_ksym_var(obj->btf);