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From:   Christian Brauner <christian.brauner@canonical.com>
Date:   Sun, 29 Apr 2018 11:59:58 +0200
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     davem@davemloft.net, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, avagin@virtuozzo.com,
        ktkhai@virtuozzo.com, serge@hallyn.com, gregkh@linuxfoundation.org
Subject: Re: [PATCH net-next 2/2 v4] netns: restrict uevents
Message-ID: <20180429095957.GA27296@gmail.com>
References: <20180428192025.2075-1-christian.brauner@ubuntu.com>
 <20180428192025.2075-3-christian.brauner@ubuntu.com>
 <87in8ad4ip.fsf@xmission.com>
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On Sat, Apr 28, 2018 at 11:23:58PM -0500, Eric W. Biederman wrote:
> 
> > +	/* fix credentials */
> > +	if (owning_user_ns != &init_user_ns) {
> > +		struct netlink_skb_parms *parms = &NETLINK_CB(skb);
> > +		kuid_t root_uid;
> > +		kgid_t root_gid;
> > +
> > +		/* fix uid */
> > +		root_uid = make_kuid(owning_user_ns, 0);
> > +		if (!uid_valid(root_uid))
> > +			root_uid = GLOBAL_ROOT_UID;
> > +		parms->creds.uid = root_uid;
> > +
> > +		/* fix gid */
> > +		root_gid = make_kgid(owning_user_ns, 0);
> > +		if (!gid_valid(root_gid))
> > +			root_gid = GLOBAL_ROOT_GID;
> > +		parms->creds.gid = root_gid;
> 
> One last nit:

Will add non-functional change and make it a v5 in a few.

Thanks!
Christian

> 
> 	You can only make the assignment if the uid is valid.
>         Leaving it GLBOAL_ROOT_UID if the composed uid is invalid.
>         AKA
> 
> 		/* fix uid */
> 		root_uid = make_kuid(owning_user_ns, 0);
> 		if (uid_valid(root_uid))
>                 	parms->creds.uid = root_uid;
> 
>                 /* fix gid */
> 		root_gid = make_kgid(owning_user_ns, 0);
>                 if (gid_valid(root_gid))
>                 	params->creds.gid = root_gid;
> 
> 
> One line shorter and I think a little clearer.  I suspect
> it even results in better code.
> 
> Eric