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

[Nikolay Aleksandrov]

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@xxxxxx>
> > > ---
> > >    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