On Wed, Oct 14, 2020 at 02:59:47PM +0200, Jason A. Donenfeld wrote:
> Hey Pablo,
>
> In 60a3815da702fd9e4759945f26cce5c47d3967ad, you added another enum
> value to nf_inet_hooks:
>
> --- a/include/uapi/linux/netfilter.h
> +++ b/include/uapi/linux/netfilter.h
> @@ -45,6 +45,7 @@ enum nf_inet_hooks {
> NF_INET_FORWARD,
> NF_INET_LOCAL_OUT,
> NF_INET_POST_ROUTING,
> + NF_INET_INGRESS,
> NF_INET_NUMHOOKS
> };
>
> That seems fine, but actually it changes the value of
> NF_INET_NUMHOOKS, which is used in struct ipt_getinfo:
>
> /* The argument to IPT_SO_GET_INFO */
> struct ipt_getinfo {
> /* Which table: caller fills this in. */
> char name[XT_TABLE_MAXNAMELEN];
>
> /* Kernel fills these in. */
> /* Which hook entry points are valid: bitmask */
> unsigned int valid_hooks;
>
> /* Hook entry points: one per netfilter hook. */
> unsigned int hook_entry[NF_INET_NUMHOOKS];
>
> /* Underflow points. */
> unsigned int underflow[NF_INET_NUMHOOKS];
>
> /* Number of entries */
> unsigned int num_entries;
>
> /* Size of entries. */
> unsigned int size;
> };
>
> This in turn makes that struct bigger, which means this check in
> net/ipv4/netfilter/ip_tables.c fails:
>
> static int get_info(struct net *net, void __user *user, const int *len)
> {
> char name[XT_TABLE_MAXNAMELEN];
> struct xt_table *t;
> int ret;
>
> if (*len != sizeof(struct ipt_getinfo))
> return -EINVAL;
>
> This is affecting my CI, which attempts to use an older iptables with
> net-next and fails with:
>
> iptables v1.8.4 (legacy): can't initialize iptables table `filter':
> Module is wrong version
> Perhaps iptables or your kernel needs to be upgraded.
>
> Is this kind of breakage okay? If there's an exception carved out for
> breaking the iptables API, just let me know, and I'll look into making
> adjustments to work around it in my CI. On the other hand, if this
> breakage was unintentional, now you know.
Oh right, I'll need a new IPT_INET_NUMHOOKS for this.
I'll submit a patch, that's for the heads up.
