Subject: Re: [PATCH net-next 9/9] netfilter: nf_tables: add support to destroy operation

From: Vlad Buslov <[email-masked]>
Date: Thu, 19 Jan 2023 09:29:50 +0200

On Wed 18 Jan 2023 at 13:32, Florian Westphal <[email-masked]> wrote:
> From: Fernando Fernandez Mancera <[email-masked]>
>
> Introduce NFT_MSG_DESTROY* message type. The destroy operation performs a
> delete operation but ignoring the ENOENT errors.
>
> This is useful for the transaction semantics, where failing to delete an
> object which does not exist results in aborting the transaction.
>
> This new command allows the transaction to proceed in case the object
> does not exist.
>
> Signed-off-by: Fernando Fernandez Mancera <[email-masked]>
> Signed-off-by: Pablo Neira Ayuso <[email-masked]>
> Signed-off-by: Florian Westphal <[email-masked]>
> ---
>  include/uapi/linux/netfilter/nf_tables.h |  14 +++
>  net/netfilter/nf_tables_api.c            | 111 +++++++++++++++++++++--
>  2 files changed, 117 insertions(+), 8 deletions(-)
>
> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> index cfa844da1ce6..ff677f3a6cad 100644
> --- a/include/uapi/linux/netfilter/nf_tables.h
> +++ b/include/uapi/linux/netfilter/nf_tables.h
> @@ -98,6 +98,13 @@ enum nft_verdicts {
>   * @NFT_MSG_GETFLOWTABLE: get flow table (enum nft_flowtable_attributes)
>   * @NFT_MSG_DELFLOWTABLE: delete flow table (enum nft_flowtable_attributes)
>   * @NFT_MSG_GETRULE_RESET: get rules and reset stateful expressions (enum nft_obj_attributes)
> + * @NFT_MSG_DESTROYTABLE: destroy a table (enum nft_table_attributes)
> + * @NFT_MSG_DESTROYCHAIN: destroy a chain (enum nft_chain_attributes)
> + * @NFT_MSG_DESTROYRULE: destroy a rule (enum nft_rule_attributes)
> + * @NFT_MSG_DESTROYSET: destroy a set (enum nft_set_attributes)
> + * @NFT_MSG_DESTROYSETELEM: destroy a set element (enum nft_set_elem_attributes)
> + * @NFT_MSG_DESTROYOBJ: destroy a stateful object (enum nft_object_attributes)
> + * @NFT_MSG_DESTROYFLOWTABLE: destroy flow table (enum nft_flowtable_attributes)
>   */
>  enum nf_tables_msg_types {
>  	NFT_MSG_NEWTABLE,
> @@ -126,6 +133,13 @@ enum nf_tables_msg_types {
>  	NFT_MSG_GETFLOWTABLE,
>  	NFT_MSG_DELFLOWTABLE,
>  	NFT_MSG_GETRULE_RESET,
> +	NFT_MSG_DESTROYTABLE,
> +	NFT_MSG_DESTROYCHAIN,
> +	NFT_MSG_DESTROYRULE,
> +	NFT_MSG_DESTROYSET,
> +	NFT_MSG_DESTROYSETELEM,
> +	NFT_MSG_DESTROYOBJ,
> +	NFT_MSG_DESTROYFLOWTABLE,
>  	NFT_MSG_MAX,
>  };
>  
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 8c09e4d12ac1..974b95dece1d 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -1401,6 +1401,10 @@ static int nf_tables_deltable(struct sk_buff *skb, const struct nfnl_info *info,
>  	}
>  
>  	if (IS_ERR(table)) {
> +		if (PTR_ERR(table) == -ENOENT &&
> +		    NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYTABLE)
> +			return 0;
> +
>  		NL_SET_BAD_ATTR(extack, attr);
>  		return PTR_ERR(table);
>  	}
> @@ -2639,6 +2643,10 @@ static int nf_tables_delchain(struct sk_buff *skb, const struct nfnl_info *info,
>  		chain = nft_chain_lookup(net, table, attr, genmask);
>  	}
>  	if (IS_ERR(chain)) {
> +		if (PTR_ERR(chain) == -ENOENT &&
> +		    NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYCHAIN)
> +			return 0;
> +
>  		NL_SET_BAD_ATTR(extack, attr);
>  		return PTR_ERR(chain);
>  	}
> @@ -3716,6 +3724,10 @@ static int nf_tables_delrule(struct sk_buff *skb, const struct nfnl_info *info,
>  		chain = nft_chain_lookup(net, table, nla[NFTA_RULE_CHAIN],
>  					 genmask);
>  		if (IS_ERR(chain)) {
> +			if (PTR_ERR(rule) == -ENOENT &&

Coverity complains that at this point rule is not initialized yet, which
looks like to be the case to me.

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