[PATCH] libbpf: check the btf_type kind to prevent error

[Ma Ke]

To prevent potential error return values, it is necessary to check the
return value of btf__type_by_id. We can add a kind checking to fix the
issue.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 430025e5dca5 ("libbpf: Add subskeleton scaffolding")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
 tools/lib/bpf/libbpf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a3be6f8fac09..d1eb45d16054 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -13850,6 +13850,9 @@ int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
 		var = btf_var_secinfos(map_type);
 		for (i = 0; i < len; i++, var++) {
 			var_type = btf__type_by_id(btf, var->type);
+			if (!var_type)
+				return libbpf_err(-ENOENT);
+
 			var_name = btf__name_by_offset(btf, var_type->name_off);
 			if (strcmp(var_name, var_skel->name) == 0) {
 				*var_skel->addr = map->mmaped + var->offset;
-- 
2.25.1