libbpf: fix memory leak in attach_tp for target-less tracepoint program

Fix sec_name memory leak if user defines target-less SEC("tp").

Fixes: 9af8efc45e ("libbpf: Allow "incomplete" basic tracing SEC() definitions")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20220516184547.3204674-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/libbpf.c

@@ -11592,16 +11592,16 @@ static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_lin
 {
 	char *sec_name, *tp_cat, *tp_name;
 
-	sec_name = strdup(prog->sec_name);
-	if (!sec_name)
-		return -ENOMEM;
-
 	*link = NULL;
 
 	/* no auto-attach for SEC("tp") or SEC("tracepoint") */
 	if (strcmp(prog->sec_name, "tp") == 0 || strcmp(prog->sec_name, "tracepoint") == 0)
 		return 0;
 
+	sec_name = strdup(prog->sec_name);
+	if (!sec_name)
+		return -ENOMEM;
+
 	/* extract "tp/<category>/<name>" or "tracepoint/<category>/<name>" */
 	if (str_has_pfx(prog->sec_name, "tp/"))
 		tp_cat = sec_name + sizeof("tp/") - 1;