Subject: Re: [PATCH v1] bpf: Add length check for SK_DIAG_BPF_STORAGE_REQ_MAP_FD parsing

From: Jakub Kicinski <[email-masked]>
Date: Mon, 24 Jul 2023 15:15:07 -0700

On Sun, 23 Jul 2023 15:54:52 +0800 Lin Ma wrote:
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index d4172534dfa8..6f1afbb394a6 100644
> --- a/net/core/bpf_sk_storage.c
> +++ b/net/core/bpf_sk_storage.c
> @@ -511,6 +511,11 @@ bpf_sk_storage_diag_alloc(const struct nlattr *nla_stgs)
>  		if (nla_type(nla) != SK_DIAG_BPF_STORAGE_REQ_MAP_FD)
>  			continue;
>  
> +		if (nla_len(nla) < sizeof(map_fd)) {
> +			err = -EINVAL;
> +			goto err_free;
> +		}

You can move this check earlier, when the attributes are getting
counted. That way we can avoid the alloc/free on error.