linux-kernel - Re: [PATCH net-next 1/3] genetlink: do not validate dump requests if there is no policy

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Message-ID: <20190502133231.GF21672@unicorn.suse.cz>
Date:   Thu, 2 May 2019 15:32:31 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Ahern <dsahern@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 1/3] genetlink: do not validate dump requests if
 there is no policy

On Thu, May 02, 2019 at 03:13:00PM +0200, Johannes Berg wrote:
> On Thu, 2019-05-02 at 15:10 +0200, Michal Kubecek wrote:
> > On Thu, May 02, 2019 at 02:51:33PM +0200, Johannes Berg wrote:
> > > On Thu, 2019-05-02 at 12:48 +0000, Michal Kubecek wrote:
> > > > Unlike do requests, dump genetlink requests now perform strict validation
> > > > by default even if the genetlink family does not set policy and maxtype
> > > > because it does validation and parsing on its own (e.g. because it wants to
> > > > allow different message format for different commands). While the null
> > > > policy will be ignored, maxtype (which would be zero) is still checked so
> > > > that any attribute will fail validation.
> > > > 
> > > > The solution is to only call __nla_validate() from genl_family_rcv_msg()
> > > > if family->maxtype is set.
> > > 
> > > D'oh. Which family was it that you found this on? I checked only ones
> > > with policy I guess.
> > 
> > It was with my ethtool netlink series (still work in progress).
> 
> Then you should probably *have* a policy to get all the other goodies
> like automatic policy export (once I repost those patches)

Wouldn't it mean effecitvely ending up with only one command (in
genetlink sense) and having to distinguish actual commands with
atributes? Even if I wanted to have just "get" and "set" command, common
policy wouldn't allow me to say which attributes are allowed for each of
them.

Michal