From: Mykyta Yatsenko <yatsenko@meta.com>
Date: Wed, 14 May 2025 11:32:20 +0000 (+0100)
Subject: libbpf: Check bpf_map_skeleton link for NULL
X-Git-Tag: v6.16-rc1~131^2~24
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=d0445d7dd3fd9b15af7564c38d7aa3cbc29778ee;p=linux-2.6-block.git

libbpf: Check bpf_map_skeleton link for NULL

Avoid dereferencing bpf_map_skeleton's link field if it's NULL.
If BPF map skeleton is created with the size, that indicates containing
link field, but the field was not actually initialized with valid
bpf_link pointer, libbpf crashes. This may happen when using libbpf-rs
skeleton.
Skeleton loading may still progress, but user needs to attach struct_ops
map separately.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250514113220.219095-1-mykyta.yatsenko5@gmail.com
---

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 617cfb9a7ff5..e9c641a2fb20 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -14102,6 +14102,12 @@ int bpf_object__attach_skeleton(struct bpf_object_skeleton *s)
 		}
 
 		link = map_skel->link;
+		if (!link) {
+			pr_warn("map '%s': BPF map skeleton link is uninitialized\n",
+				bpf_map__name(map));
+			continue;
+		}
+
 		if (*link)
 			continue;