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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Andrii Nakryiko <andrii@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Yonghong Song <yhs@fb.com>, Sasha Levin <sashal@kernel.org>,
        daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH AUTOSEL 5.16 010/217] libbpf: Validate that .BTF and .BTF.ext sections contain data
Date:   Mon, 17 Jan 2022 21:16:13 -0500
Message-Id: <20220118021940.1942199-10-sashal@kernel.org>
In-Reply-To: <20220118021940.1942199-1-sashal@kernel.org>
References: <20220118021940.1942199-1-sashal@kernel.org>
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From: Andrii Nakryiko <andrii@kernel.org>

[ Upstream commit 62554d52e71797eefa3fc15b54008038837bb2d4 ]

.BTF and .BTF.ext ELF sections should have SHT_PROGBITS type and contain
data. If they are not, ELF is invalid or corrupted, so bail out.
Otherwise this can lead to data->d_buf being NULL and SIGSEGV later on.
Reported by oss-fuzz project.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211103173213.1376990-4-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/lib/bpf/libbpf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 18651e11b9ba3..7d27152dfb3a6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3270,8 +3270,12 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 		} else if (strcmp(name, MAPS_ELF_SEC) == 0) {
 			obj->efile.btf_maps_shndx = idx;
 		} else if (strcmp(name, BTF_ELF_SEC) == 0) {
+			if (sh->sh_type != SHT_PROGBITS)
+				return -LIBBPF_ERRNO__FORMAT;
 			btf_data = data;
 		} else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
+			if (sh->sh_type != SHT_PROGBITS)
+				return -LIBBPF_ERRNO__FORMAT;
 			btf_ext_data = data;
 		} else if (sh->sh_type == SHT_SYMTAB) {
 			/* already processed during the first pass above */
-- 
2.34.1