| Message ID | 20210210120425.53438-1-lmb@cloudflare.com |
|---|---|
| Headers | show |
| Series | Expose network namespace cookies to user space | expand |
On Wed, Feb 10, 2021 at 12:04:23PM +0000, Lorenz Bauer wrote: > Network namespaces have a globally unique non-zero identifier aka a > cookie, in line with socket cookies. Add an ioctl to retrieve the > cookie from user space without going via BPF. > > Cc: linux-api@vger.kernel.org > Signed-off-by: Lorenz Bauer <lmb@cloudflare.com> > --- > fs/nsfs.c | 9 +++++++++ > include/net/net_namespace.h | 11 +++++++++++ > include/uapi/linux/nsfs.h | 2 ++ > 3 files changed, 22 insertions(+) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 800c1d0eb0d0..d7865e39c049 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -11,6 +11,7 @@ > #include <linux/user_namespace.h> > #include <linux/nsfs.h> > #include <linux/uaccess.h> > +#include <net/net_namespace.h> > > #include "internal.h" > > @@ -191,6 +192,8 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, > struct user_namespace *user_ns; > struct ns_common *ns = get_proc_ns(file_inode(filp)); > uid_t __user *argp; > + struct net *net_ns; > + u64 cookie; > uid_t uid; > > switch (ioctl) { > @@ -209,6 +212,12 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, > argp = (uid_t __user *) arg; > uid = from_kuid_munged(current_user_ns(), user_ns->owner); > return put_user(uid, argp); > + case NS_GET_COOKIE: > + if (ns->ops->type != CLONE_NEWNET) > + return -EINVAL; > + net_ns = container_of(ns, struct net, ns); > + cookie = net_gen_cookie(net_ns); > + return put_user(cookie, (u64 __user *)arg); Hey Lorenz, Just to make sure: is it intentional that any user can retrieve the cookie associated with any network namespace, i.e. you don't require any form of permission checking in the owning user namespace of the network namespace? Christian
On Mon, 1 Mar 2021 at 10:04, Christian Brauner <christian.brauner@ubuntu.com> wrote: > > Hey Lorenz, > > Just to make sure: is it intentional that any user can retrieve the > cookie associated with any network namespace, i.e. you don't require any > form of permission checking in the owning user namespace of the network > namespace? > > Christian Hi Christian, I've decided to drop the patch set for now, but that was my intention, yes. Is there a downside I'm not aware of? Lorenz -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
On Tue, Mar 02, 2021 at 09:47:10AM +0000, Lorenz Bauer wrote: > On Mon, 1 Mar 2021 at 10:04, Christian Brauner > <christian.brauner@ubuntu.com> wrote: > > > > Hey Lorenz, > > > > Just to make sure: is it intentional that any user can retrieve the > > cookie associated with any network namespace, i.e. you don't require any > > form of permission checking in the owning user namespace of the network > > namespace? > > > > Christian > > Hi Christian, > > I've decided to drop the patch set for now, but that was my intention, yes. Is > there a downside I'm not aware of? It depends on whether this cookie is in any way security or at least information sensitive. For example, would leaking it between unprivileged containers with different user+network namespace pairs allow one container to gain access to information about the other container that it shouldn't. Christian