Re: [PATCH] net: fix oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled

On Mon, May 31, 2021 at 08:30:58AM +0000, David Laight wrote:

From: Cong Wang

quoted

Sent: 29 May 2021 20:15

On Fri, May 28, 2021 at 11:08 PM Changbin Du [off-list ref] wrote:

quoted

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?

Here is the new fix that reject creating indoe for disabled ns.

--- a/fs/nsfs.c
+++ b/fs/nsfs.c

@@ -62,6 +62,10 @@ static int __ns_get_path(struct path *path, struct ns_common *ns)
        struct inode *inode;
        unsigned long d;
 
+       /* In case the namespace is not actually enabled. */
+       if (!ns->ops)
+               return -EOPNOTSUPP;

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

-- 
Cheers,
Changbin Du