libbpf: Fix accessing BTF.ext core_relo header

Update btf_ext_parse_info() to ensure the core_relo header is present
before reading its fields. This avoids a potential buffer read overflow
reported by the OSS Fuzz project.

Fixes: cf579164e9ea ("libbpf: Support BTF.ext loading and output in either endianness")
Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://issues.oss-fuzz.com/issues/388905046
Link: https://lore.kernel.org/bpf/20250125065236.2603346-1-itugrok@yahoo.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 48c66f3a9200210c23a27a94cc89f279bd75e67e..560b519f820e24ea4b60453b85fdd6398cae4d0c 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -3015,8 +3015,6 @@ static int btf_ext_parse_info(struct btf_ext *btf_ext, bool is_native)
                .desc = "line_info",
        };
        struct btf_ext_sec_info_param core_relo = {
-               .off = btf_ext->hdr->core_relo_off,
-               .len = btf_ext->hdr->core_relo_len,
                .min_rec_size = sizeof(struct bpf_core_relo),
                .ext_info = &btf_ext->core_relo_info,
                .desc = "core_relo",
@@ -3034,6 +3032,8 @@ static int btf_ext_parse_info(struct btf_ext *btf_ext, bool is_native)
        if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
                return 0; /* skip core relos parsing */
 
+       core_relo.off = btf_ext->hdr->core_relo_off;
+       core_relo.len = btf_ext->hdr->core_relo_len;
        err = btf_ext_parse_sec_info(btf_ext, &core_relo, is_native);
        if (err)
                return err;