linux-kernel - [PATCH AUTOSEL 5.16 008/217] libbpf: Detect corrupted ELF symbols section

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Message-Id: <20220118021940.1942199-8-sashal@kernel.org>
Date:   Mon, 17 Jan 2022 21:16:11 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>, Sasha Levin <sashal@...nel.org>,
        daniel@...earbox.net, netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.16 008/217] libbpf: Detect corrupted ELF symbols section

From: Andrii Nakryiko <andrii@...nel.org>

[ Upstream commit 833907876be55205d0ec153dcd819c014404ee16 ]

Prevent divide-by-zero if ELF is corrupted and has zero sh_entsize.
Reported by oss-fuzz project.

Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Yonghong Song <yhs@...com>
Link: https://lore.kernel.org/bpf/20211103173213.1376990-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7c74342bb6680..b5bf1c074832e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3555,7 +3555,7 @@ 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);
-- 
2.34.1