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

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Message-ID: <ZQ2GHS2r1W77iE50@u-jnixdorf.ads.avm.de>
Date:   Fri, 22 Sep 2023 14:18:37 +0200
From:   Johannes Nixdorf <jnixdorf-oss@....de>
To:     Nikolay Aleksandrov <razor@...ckwall.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>, David Ahern <dsahern@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ido Schimmel <idosch@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>, Shuah Khan <shuah@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v4 2/6] net: bridge: Set strict_start_type for
 br_policy

On Thu, Sep 21, 2023 at 01:14:43PM +0300, Nikolay Aleksandrov wrote:
> 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@....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.

Ok. I've changed it locally for v5.