[Bridge] [PATCH] netfilter: nft_meta: fix bridge port vlan ID selector

[Nikolay Aleksandrov]

On 03/07/2019 15:53, Nikolay Aleksandrov wrote:
> On 03/07/2019 15:48, Nikolay Aleksandrov wrote:
>> On 03/07/2019 15:40, Pablo Neira Ayuso wrote:
>>> Use br_vlan_enabled() and br_vlan_get_pvid() helpers as Nikolay
>>> suggests.
>>>
>>> Rename NFT_META_BRI_PVID to NFT_META_BRI_IIFPVID before this patch hits
>>> the 5.3 release cycle, to leave room for matching for the output bridge
>>> port in the future.
>>>
>>> Reported-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
>>> Fixes: da4f10a4265b ("netfilter: nft_meta: add NFT_META_BRI_PVID support")
>>> Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
>>> ---
>>>  include/uapi/linux/netfilter/nf_tables.h |  4 ++--
>>>  net/netfilter/nft_meta.c                 | 17 ++++++++++-------
>>>  2 files changed, 12 insertions(+), 9 deletions(-)
>>>
>>
>> Ah actually I might've hurried too much with the suggestion, we don't have a helper to
>> check through a port if vlan filtering has been enabled. The helper assumes that
>> the device is a bridge. So below you'll have to use p->br->dev with br_vlan_enabled().
>> And in fact the proper way would be to get the "upper" device via netdev_master_upper_dev_get()
>> and then to use that in order to avoid direct dereferencing.
>>
> 
> Sorry for the multiple replies, I just noticed this is running from fast-path so you'll
> have to use the _rcu variant and check for null since they are unlinked before the port
> flag is removed in del_nbp() (bridge/bf_if.c).
> 

And then just scratch all of that and use p->br->dev directly, I saw it's already dereferenced before. :)
Apologies for the noise.

>>> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
>>> index 8859535031e2..8a1bd0b1ec8c 100644
>>> --- a/include/uapi/linux/netfilter/nf_tables.h
>>> +++ b/include/uapi/linux/netfilter/nf_tables.h
>>> @@ -795,7 +795,7 @@ enum nft_exthdr_attributes {
>>>   * @NFT_META_SECPATH: boolean, secpath_exists (!!skb->sp)
>>>   * @NFT_META_IIFKIND: packet input interface kind name (dev->rtnl_link_ops->kind)
>>>   * @NFT_META_OIFKIND: packet output interface kind name (dev->rtnl_link_ops->kind)
>>> - * @NFT_META_BRI_PVID: packet input bridge port pvid
>>> + * @NFT_META_BRI_IIFPVID: packet input bridge port pvid
>>>   */
>>>  enum nft_meta_keys {
>>>  	NFT_META_LEN,
>>> @@ -826,7 +826,7 @@ enum nft_meta_keys {
>>>  	NFT_META_SECPATH,
>>>  	NFT_META_IIFKIND,
>>>  	NFT_META_OIFKIND,
>>> -	NFT_META_BRI_PVID,
>>> +	NFT_META_BRI_IIFPVID,
>>>  };
>>>  
>>>  /**
>>> diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
>>> index 4f8116de70f8..b8d8adc0852e 100644
>>> --- a/net/netfilter/nft_meta.c
>>> +++ b/net/netfilter/nft_meta.c
>>> @@ -240,14 +240,17 @@ void nft_meta_get_eval(const struct nft_expr *expr,
>>>  			goto err;
>>>  		strncpy((char *)dest, p->br->dev->name, IFNAMSIZ);
>>>  		return;
>>> -	case NFT_META_BRI_PVID:
>>> +	case NFT_META_BRI_IIFPVID: {
>>> +		u16 p_pvid;
>>> +
>>>  		if (in == NULL || (p = br_port_get_rtnl_rcu(in)) == NULL)
>>>  			goto err;
>>> -		if (br_opt_get(p->br, BROPT_VLAN_ENABLED)) {
>>> -			nft_reg_store16(dest, br_get_pvid(nbp_vlan_group_rcu(p)));
>>> -			return;
>>> -		}
>>> -		goto err;
>>> +		if (!br_vlan_enabled(in))
>>> +			goto err;
>>> +		br_vlan_get_pvid(in, &p_pvid);
>>> +		nft_reg_store16(dest, p_pvid);
>>> +		return;
>>> +	}
>>>  #endif
>>>  	case NFT_META_IIFKIND:
>>>  		if (in == NULL || in->rtnl_link_ops == NULL)
>>> @@ -375,7 +378,7 @@ static int nft_meta_get_init(const struct nft_ctx *ctx,
>>>  			return -EOPNOTSUPP;
>>>  		len = IFNAMSIZ;
>>>  		break;
>>> -	case NFT_META_BRI_PVID:
>>> +	case NFT_META_BRI_IIFPVID:
>>>  		if (ctx->family != NFPROTO_BRIDGE)
>>>  			return -EOPNOTSUPP;
>>>  		len = sizeof(u16);
>>>
>>
>