[PATCH] libbpf: check for empty BTF data section in btf_parse_elf

[Ihor Solodrai <ihor.solodrai@linux.dev>]

A valid ELF file may contain a SHT_NOBITS .BTF section. This case is
not handled correctly in btf_parse_elf, which leads to a segfault.

Add a null check for a buffer returned by elf_getdata() before
proceeding with its processing.

Bug report: https://github.com/libbpf/libbpf/issues/894

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/lib/bpf/btf.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 38bc6b14b066..90599f0311bd 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1201,6 +1201,12 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 		goto done;
 	}
 
+	if (!secs.btf_data->d_buf) {
+		pr_warn("BTF data is empty in %s\n", path);
+		err = -ENODATA;
+		goto done;
+	}
+
 	if (secs.btf_base_data) {
 		dist_base_btf = btf_new(secs.btf_base_data->d_buf, secs.btf_base_data->d_size,
 					NULL);
-- 
2.49.0