Re: [PATCH,nf-next RFC 1/2] netfilter: nf_tables: add nft_setelem_parse_key()

[Stefano Brivio <sbrivio@redhat.com>]

Hi Pablo,

Just two nits:

On Mon,  2 Dec 2019 14:14:06 +0100
Pablo Neira Ayuso <pablo@netfilter.org> wrote:

> Add helper function to parse the set element key netlink attribute.
> 
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> ---
>  net/netfilter/nf_tables_api.c | 56 ++++++++++++++++++++++++-------------------
>  1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 0db2784fee9a..13e291fac26f 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -4490,11 +4490,31 @@ static int nft_setelem_parse_flags(const struct nft_set *set,
>  	return 0;
>  }
>  
> +static int nft_setelem_parse_key(struct nft_ctx *ctx, struct nft_set *set,
> +				 struct nft_data *key, struct nlattr *attr)
> +{
> +	struct nft_data_desc desc;
> +	int err;
> +
> +	err = nft_data_init(ctx, key, sizeof(*key), &desc, attr);
> +	if (err < 0)
> +		goto err1;
> +
> +	err = -EINVAL;
> +	if (desc.type != NFT_DATA_VALUE || desc.len != set->klen)
> +		goto err2;
> +
> +	return 0;
> +err2:
> +	nft_data_release(key, desc.type);
> +err1:
> +	return err;
> +}
> +
>  static int nft_get_set_elem(struct nft_ctx *ctx, struct nft_set *set,
>  			    const struct nlattr *attr)
>  {
>  	struct nlattr *nla[NFTA_SET_ELEM_MAX + 1];
> -	struct nft_data_desc desc;
>  	struct nft_set_elem elem;
>  	struct sk_buff *skb;
>  	uint32_t flags = 0;
> @@ -4513,15 +4533,11 @@ static int nft_get_set_elem(struct nft_ctx *ctx, struct nft_set *set,
>  	if (err < 0)
>  		return err;
>  
> -	err = nft_data_init(ctx, &elem.key.val, sizeof(elem.key), &desc,
> -			    nla[NFTA_SET_ELEM_KEY]);
> +	err = nft_setelem_parse_key(ctx, set, &elem.key.val,
> +				    nla[NFTA_SET_ELEM_KEY]);
>  	if (err < 0)
>  		return err;
>  
> -	err = -EINVAL;
> -	if (desc.type != NFT_DATA_VALUE || desc.len != set->klen)
> -		return err;
> -
>  	priv = set->ops->get(ctx->net, set, &elem, flags);
>  	if (IS_ERR(priv))
>  		return PTR_ERR(priv);
> @@ -4720,13 +4736,13 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
>  {
>  	struct nlattr *nla[NFTA_SET_ELEM_MAX + 1];
>  	u8 genmask = nft_genmask_next(ctx->net);
> -	struct nft_data_desc d1, d2;
>  	struct nft_set_ext_tmpl tmpl;
>  	struct nft_set_ext *ext, *ext2;
>  	struct nft_set_elem elem;
>  	struct nft_set_binding *binding;
>  	struct nft_object *obj = NULL;
>  	struct nft_userdata *udata;
> +	struct nft_data_desc d2;

At this point, this could simply be desc, or data_desc.

>  	struct nft_data data;
>  	enum nft_registers dreg;
>  	struct nft_trans *trans;
> @@ -4792,15 +4808,12 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
>  			return err;
>  	}
>  
> -	err = nft_data_init(ctx, &elem.key.val, sizeof(elem.key), &d1,
> -			    nla[NFTA_SET_ELEM_KEY]);
> +	err = nft_setelem_parse_key(ctx, set, &elem.key.val,
> +				    nla[NFTA_SET_ELEM_KEY]);
>  	if (err < 0)
>  		goto err1;
> -	err = -EINVAL;
> -	if (d1.type != NFT_DATA_VALUE || d1.len != set->klen)
> -		goto err2;
>  
> -	nft_set_ext_add_length(&tmpl, NFT_SET_EXT_KEY, d1.len);
> +	nft_set_ext_add_length(&tmpl, NFT_SET_EXT_KEY, set->klen);
>  	if (timeout > 0) {
>  		nft_set_ext_add(&tmpl, NFT_SET_EXT_EXPIRATION);
>  		if (timeout != set->timeout)
> @@ -4942,7 +4955,7 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
>  	if (nla[NFTA_SET_ELEM_DATA] != NULL)
>  		nft_data_release(&data, d2.type);
>  err2:
> -	nft_data_release(&elem.key.val, d1.type);
> +	nft_data_release(&elem.key.val, NFT_DATA_VALUE);
>  err1:
>  	return err;
>  }
> @@ -5038,7 +5051,6 @@ static int nft_del_setelem(struct nft_ctx *ctx, struct nft_set *set,
>  {
>  	struct nlattr *nla[NFTA_SET_ELEM_MAX + 1];
>  	struct nft_set_ext_tmpl tmpl;
> -	struct nft_data_desc desc;
>  	struct nft_set_elem elem;
>  	struct nft_set_ext *ext;
>  	struct nft_trans *trans;
> @@ -5063,16 +5075,12 @@ static int nft_del_setelem(struct nft_ctx *ctx, struct nft_set *set,
>  	if (flags != 0)
>  		nft_set_ext_add(&tmpl, NFT_SET_EXT_FLAGS);
>  
> -	err = nft_data_init(ctx, &elem.key.val, sizeof(elem.key), &desc,
> -			    nla[NFTA_SET_ELEM_KEY]);
> +	err = nft_setelem_parse_key(ctx, set, &elem.key.val,
> +				    nla[NFTA_SET_ELEM_KEY]);
>  	if (err < 0)
>  		goto err1;
>  
> -	err = -EINVAL;
> -	if (desc.type != NFT_DATA_VALUE || desc.len != set->klen)
> -		goto err2;
> -
> -	nft_set_ext_add_length(&tmpl, NFT_SET_EXT_KEY, desc.len);
> +	nft_set_ext_add_length(&tmpl, NFT_SET_EXT_KEY, set->klen);
>  
>  	err = -ENOMEM;
>  	elem.priv = nft_set_elem_init(set, &tmpl, elem.key.val.data, NULL, 0,
> @@ -5109,7 +5117,7 @@ static int nft_del_setelem(struct nft_ctx *ctx, struct nft_set *set,
>  err3:
>  	kfree(elem.priv);
>  err2:
> -	nft_data_release(&elem.key.val, desc.type);
> +	nft_data_release(&elem.key.val, NFT_DATA_VALUE);

I'm not sure if this can actually happen, but in
nft_setelem_parse_key() you are checking that the type is
NFT_DATA_VALUE, and returning error if it's not.

If the type is not NFT_DATA_VALUE, I guess we shouldn't pass
NFT_DATA_VALUE to nft_data_release() here.

Maybe nft_setelem_parse_key() could clean up after itself on error.
After all, nft_data_init() is now called from there.

>  err1:
>  	return err;
>  }

Otherwise, it looks good to me. Note that, while I'm working on
integrating this with the rest of kernel changes right now, I haven't
tested it in any way (that needs your changes for userspace).

-- 
Stefano