libbpf: Potential NULL dereference in usdt_manager_attach_usdt()

link could be null but still dereference bpf_link__destroy(&link->link)
and it will lead to a null pointer access.

Signed-off-by: Haowen Bai <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: Lotte-Bai

tools/lib/bpf/usdt.c

@@ -1071,8 +1071,8 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
 	return &link->link;
 
 err_out:
-	bpf_link__destroy(&link->link);
-
+	if (link)
+		bpf_link__destroy(&link->link);
 	free(targets);
 	hashmap__free(specs_hash);
 	if (elf)