[ABI REVIEW][PATCH 0/8] Namespace file descriptors

[Andrew Lutomirski]

Eric W. Biederman wrote:
> Introduce file for manipulating namespaces and related syscalls.
> files:
> /proc/self/ns/<nstype>
> 
> syscalls:
> int setns(unsigned long nstype, int fd);
> socketat(int nsfd, int family, int type, int protocol);
> 

How does security work?  Are there different kinds of fd that give (say) pin-the-namespace permission, socketat permission, and setns permission?

--Andy

> Netlink attribute:
> IFLA_NS_FD int fd.
> 
> Name space file descriptors address three specific problems that
> can make namespaces hard to work with.
> - Namespaces require a dedicated process to pin them in memory.
> - It is not possible to use a namespace unless you are the child of the
>   original creator.
> - Namespaces don't have names that userspace can use to talk about them.
> 
> Opening of the /proc/self/ns/<nstype> files return a file descriptor
> that can be used to talk about a specific namespace, and to keep the
> specified namespace alive.
> 
> /proc/self/ns/<nstype> can be bind mounted as:
> mount --bind /proc/self/ns/net /some/filesystem/path
> to keep the namespace alive as long as the mount exists.
> 
> setns() as a companion to unshare allows changing the namespace
> of the current process, being able to unshare the namespace is
> a requirement.
> 
> There are two primary envisioned uses for this functionality.
> o ``Entering'' an existing container.
> o Allowing multiple network namespaces to be in use at once on
>   the same machine, without requiring elaborate infrastructure.
> 
> Overall this received positive reviews on the containers list but this
> needs a wider review of the ABI as this is pretty fundamental kernel
> functionality.
> 
> 
> I have left out the pid namespaces bits for the moment because the pid
> namespace still needs work before it is safe to unshare, and my concern
> at the moment is ensuring the system calls seem reasonable.
> 
> Eric W. Biederman (8):
>       ns: proc files for namespace naming policy.
>       ns: Introduce the setns syscall
>       ns proc: Add support for the network namespace.
>       ns proc: Add support for the uts namespace
>       ns proc: Add support for the ipc namespace
>       ns proc: Add support for the mount namespace
>       net: Allow setting the network namespace by fd
>       net: Implement socketat.
> 
> ---
>  fs/namespace.c              |   57 +++++++++++++
>  fs/proc/Makefile            |    1 +
>  fs/proc/base.c              |   22 +++---
>  fs/proc/inode.c             |    7 ++
>  fs/proc/internal.h          |   18 ++++
>  fs/proc/namespaces.c        |  193 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/if_link.h     |    1 +
>  include/linux/proc_fs.h     |   20 +++++
>  include/net/net_namespace.h |    1 +
>  ipc/namespace.c             |   31 +++++++
>  kernel/nsproxy.c            |   39 +++++++++
>  kernel/utsname.c            |   32 +++++++
>  net/core/net_namespace.c    |   56 +++++++++++++
>  net/core/rtnetlink.c        |    4 +-
>  net/socket.c                |   26 ++++++-
>  15 files changed, 494 insertions(+), 14 deletions(-)
>