Re: [PATCH net-next v4 2/6] net: bridge: Set strict_start_type for br_policy

Nikolay Aleksandrov
2023-09-21T21:57:26Z

On 9/21/23 10:23, Johannes Nixdorf wrote:
> On Wed, Sep 20, 2023 at 01:46:02PM +0300, Nikolay Aleksandrov wrote:
>> On 9/19/23 11:12, Johannes Nixdorf wrote:
>>> Set any new attributes added to br_policy to be parsed strictly, to
>>> prevent userspace from passing garbage.
>>>
>>> Signed-off-by: Johannes Nixdorf <jnixdorf-oss@avm.de>
>>> ---
>>> net/bridge/br_netlink.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>>> index 10f0d33d8ccf..505683ef9a26 100644
>>> --- a/net/bridge/br_netlink.c
>>> +++ b/net/bridge/br_netlink.c
>>> @@ -1229,6 +1229,8 @@ static size_t br_port_get_slave_size(const struct net_device *brdev,
>>> }
>>> static const struct nla_policy br_policy[IFLA_BR_MAX + 1] = {
>>> + [IFLA_BR_UNSPEC] = { .strict_start_type =
>>> + IFLA_BR_MCAST_QUERIER_STATE + 1 },
>>> [IFLA_BR_FORWARD_DELAY] = { .type = NLA_U32 },
>>> [IFLA_BR_HELLO_TIME] = { .type = NLA_U32 },
>>> [IFLA_BR_MAX_AGE] = { .type = NLA_U32 },
>>>
>>
>> instead of IFLA_BR_MCAST_QUERIER_STATE + 1, why not move around the patch
>> and just use the new attribute name?
>> These are uapi, they won't change.
>
> I wanted to avoid having a state between the two commits where the new
> attributes are already added, but not yet strictly verified. Otherwise
> they would present a slightly different UAPI at that one commit boundary
> than after this commit.
>

That's not really a problem, the attribute is the same.

> This is also not the only place in the kernel where strict_start_type
> is specified that way. See e.g. commit c00041cf1cb8 ("net: bridge: Set
> strict_start_type at two policies"), even though that seems mostly be
> done to turn on strict_start_type preemtively, not in the same series
> that adds the new attribute.

Please, just use the new attribute to be more explicit where the strict
parsing starts.

Thanks,
Nik