Re: [PATCH nf] netfilter: nf_tables: report error if stateful obj's name is truncated

[Patrick PIGNOL <patrick.pignol@gmail.com>]

Le 19/01/2017 à 15:41, Liping Zhang a écrit :
> The nft table name's size is limited at this place:
> static const struct nla_policy nft_table_policy[NFTA_TABLE_MAX + 1] = {
>          [NFTA_TABLE_NAME] = { .type = NLA_STRING,
>                                                     .len =
> NFT_TABLE_MAXNAMELEN - 1 },
>
> If NFTA_CHAIN_TABLE's size exceeded 31, nf_tables_table_lookup will
> fail eventually.
>
Why ? :


typedef unsigned short __u16; // minimum MaxValue = 65535

  /*
*  <------- NLA_HDRLEN ------> <-- NLA_ALIGN(payload)-->
* +---------------------+- - -+- - - - - - - - - -+- - -+
* |        Header       | Pad |     Payload     | Pad |
* |   (struct nlattr)   | ing |                        | ing |
* +---------------------+- - -+- - - - - - - - - -+- - -+
*  <-------------- nlattr->nla_len --------------> // Payload minimum 
MaxValue = 65535 - (at least)32 = 65503
*/

struct nlattr {
         __u16           nla_len;
         __u16           nla_type;
};

#define NFT_SET_MAXNAMELEN      32  // <- Why 32 ? Why not 65535 or 65503