bpf: don't leak memory in bpf getsockopt when optlen == 0

optlen == 0 indicates that the kernel should ignore BPF buffer
and use the original one from the user. We, however, forget
to free the temporary buffer that we've allocated for BPF.

Reported-by: Martin KaFai Lau <[email protected]>
Fixes: d8fe449 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE")
Signed-off-by: Stanislav Fomichev <[email protected]>

Author: fomichev

kernel/bpf/cgroup.c

@@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 	}
 
 out:
-	if (ret)
+	if (*kernel_optval == NULL)
 		sockopt_free_buf(&ctx);
 	return ret;
 }