linux-kernel - RE: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET

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Date:   Mon, 31 May 2021 08:30:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Cong Wang' <xiyou.wangcong@...il.com>,
        Changbin Du <changbin.du@...il.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kici nski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: RE: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS
 is disabled

From: Cong Wang
> Sent: 29 May 2021 20:15
> 
> On Fri, May 28, 2021 at 11:08 PM Changbin Du <changbin.du@...il.com> wrote:
> > diff --git a/net/socket.c b/net/socket.c
> > index 27e3e7d53f8e..644b46112d35 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -1149,11 +1149,15 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
> >                         mutex_unlock(&vlan_ioctl_mutex);
> >                         break;
> >                 case SIOCGSKNS:
> > +#ifdef CONFIG_NET_NS
> >                         err = -EPERM;
> >                         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> >                                 break;
> >
> >                         err = open_related_ns(&net->ns, get_net_ns);
> > +#else
> > +                       err = -ENOTSUPP;
> > +#endif
> 
> I wonder if it is easier if we just reject ns->ops==NULL case
> in open_related_ns(). For 1) we can save an ugly #ifdef here;
> 2) drivers/net/tun.c has the same bugs.

If CONFIG_NET_NS is unset then why not make both ns_capable()
and open_related_ns() unconditionally return -ENOTSUPP?

	David

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