Quoting Andrey Vagin (avagin@xxxxxxxxxx):
> On Tue, Aug 30, 2016 at 7:41 PM, Serge E. Hallyn <serge@xxxxxxxxxx> wrote:
> > On Fri, Aug 26, 2016 at 04:08:08PM -0700, Andrei Vagin wrote:
> >> From: Andrey Vagin <avagin@xxxxxxxxxx>
> >>
> >> Return -EPERM if an owning user namespace is outside of a process
> >> current user namespace.
> >>
> >> v2: In a first version ns_get_owner returned ENOENT for init_user_ns.
> >> This special cases was removed from this version. There is nothing
> >> outside of init_user_ns, so we can return EPERM.
> >>
> >> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
> >> ---
> >> fs/namespace.c | 6 ++++++
> >> include/linux/proc_ns.h | 1 +
> >> include/linux/user_namespace.h | 7 +++++++
> >> ipc/namespace.c | 6 ++++++
> >> kernel/cgroup.c | 6 ++++++
> >> kernel/pid_namespace.c | 6 ++++++
> >> kernel/user_namespace.c | 24 ++++++++++++++++++++++++
> >> kernel/utsname.c | 6 ++++++
> >> net/core/net_namespace.c | 6 ++++++
> >> 9 files changed, 68 insertions(+)
> >>
> >> diff --git a/fs/namespace.c b/fs/namespace.c
> >> index 491b8f3..f985817 100644
> >> --- a/fs/namespace.c
> >> +++ b/fs/namespace.c
> >> @@ -3368,10 +3368,16 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> >> return 0;
> >> }
> >>
> >> +static struct user_namespace *mntns_get_owner(struct ns_common *ns)
> >> +{
> >> + return to_mnt_ns(ns)->user_ns;
> >
> > Hi - sorry to be pedantic here, but *_get_owner makes me think
> > it will grab a reference too. A bit unfortunate, maybe it doesn't
> > matter, but would mntns_owner(), netns_owner(), etc be better?
>
> Actually it looks reasonable. Especially, when we have get_parent()
> which grabs a reference.
>
> Serge, could you look at the attached patch? I will need to rebase
> other patches, if we accept this patch.
>
> Thanks,
> Andrei
> From 423b2226dc9bcfefccbec21663e9287addd67e0f Mon Sep 17 00:00:00 2001
> From: Andrey Vagin <avagin@xxxxxxxxxx>
> Date: Tue, 12 Jul 2016 15:32:36 -0700
> Subject: [PATCH] kernel: add a helper to get an owning user namespace for a
> namespace
>
> Return -EPERM if an owning user namespace is outside of a process
> current user namespace.
>
> v2: In a first version ns_get_owner returned ENOENT for init_user_ns.
> This special cases was removed from this version. There is nothing
> outside of init_user_ns, so we can return EPERM.
> v3: rename ns->get_owner() to ns->owner(). get_* usually means that it
> grabs a reference.
Thanks, that should make it easier for a simpleminded fool
like myself to follow the references :)
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
> ---
> fs/namespace.c | 6 ++++++
> include/linux/proc_ns.h | 1 +
> include/linux/user_namespace.h | 7 +++++++
> ipc/namespace.c | 6 ++++++
> kernel/cgroup.c | 6 ++++++
> kernel/pid_namespace.c | 6 ++++++
> kernel/user_namespace.c | 24 ++++++++++++++++++++++++
> kernel/utsname.c | 6 ++++++
> net/core/net_namespace.c | 6 ++++++
> 9 files changed, 68 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 491b8f3..dd27ce4 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -3368,10 +3368,16 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> return 0;
> }
>
> +static struct user_namespace *mntns_owner(struct ns_common *ns)
> +{
> + return to_mnt_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations mntns_operations = {
> .name = "mnt",
> .type = CLONE_NEWNS,
> .get = mntns_get,
> .put = mntns_put,
> .install = mntns_install,
> + .owner = mntns_owner,
> };
> diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
> index de0e771..ca85a43 100644
> --- a/include/linux/proc_ns.h
> +++ b/include/linux/proc_ns.h
> @@ -18,6 +18,7 @@ struct proc_ns_operations {
> struct ns_common *(*get)(struct task_struct *task);
> void (*put)(struct ns_common *ns);
> int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);
> + struct user_namespace *(*owner)(struct ns_common *ns);
> };
>
> extern const struct proc_ns_operations netns_operations;
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index 30ffe10..eb209d4 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -106,6 +106,8 @@ extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t,
> extern int proc_setgroups_show(struct seq_file *m, void *v);
> extern bool userns_may_setgroups(const struct user_namespace *ns);
> extern bool current_in_userns(const struct user_namespace *target_ns);
> +
> +struct ns_common *ns_get_owner(struct ns_common *ns);
> #else
>
> static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
> @@ -139,6 +141,11 @@ static inline bool current_in_userns(const struct user_namespace *target_ns)
> {
> return true;
> }
> +
> +static inline struct ns_common *ns_get_owner(struct ns_common *ns)
> +{
> + return ERR_PTR(-EPERM);
> +}
> #endif
>
> #endif /* _LINUX_USER_H */
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index 7309142..465c981 100644
> --- a/ipc/namespace.c
> +++ b/ipc/namespace.c
> @@ -188,10 +188,16 @@ static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
> return 0;
> }
>
> +static struct user_namespace *ipcns_owner(struct ns_common *ns)
> +{
> + return to_ipc_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations ipcns_operations = {
> .name = "ipc",
> .type = CLONE_NEWIPC,
> .get = ipcns_get,
> .put = ipcns_put,
> .install = ipcns_install,
> + .owner = ipcns_owner,
> };
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index e9e4427..2665b58 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -6421,12 +6421,18 @@ static void cgroupns_put(struct ns_common *ns)
> put_cgroup_ns(to_cg_ns(ns));
> }
>
> +static struct user_namespace *cgroupns_owner(struct ns_common *ns)
> +{
> + return to_cg_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations cgroupns_operations = {
> .name = "cgroup",
> .type = CLONE_NEWCGROUP,
> .get = cgroupns_get,
> .put = cgroupns_put,
> .install = cgroupns_install,
> + .owner = cgroupns_owner,
> };
>
> static __init int cgroup_namespaces_init(void)
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 30a7f33..c18f0f4f 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -405,12 +405,18 @@ static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> return 0;
> }
>
> +static struct user_namespace *pidns_owner(struct ns_common *ns)
> +{
> + return to_pid_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations pidns_operations = {
> .name = "pid",
> .type = CLONE_NEWPID,
> .get = pidns_get,
> .put = pidns_put,
> .install = pidns_install,
> + .owner = pidns_owner,
> };
>
> static __init int pid_namespaces_init(void)
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 0edafe3..42a64d5 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -1050,12 +1050,36 @@ static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> return commit_creds(cred);
> }
>
> +struct ns_common *ns_get_owner(struct ns_common *ns)
> +{
> + struct user_namespace *my_user_ns = current_user_ns();
> + struct user_namespace *owner, *p;
> +
> + /* See if the owner is in the current user namespace */
> + owner = p = ns->ops->owner(ns);
> + for (;;) {
> + if (!p)
> + return ERR_PTR(-EPERM);
> + if (p == my_user_ns)
> + break;
> + p = p->parent;
> + }
> +
> + return &get_user_ns(owner)->ns;
> +}
> +
> +static struct user_namespace *userns_owner(struct ns_common *ns)
> +{
> + return to_user_ns(ns)->parent;
> +}
> +
> const struct proc_ns_operations userns_operations = {
> .name = "user",
> .type = CLONE_NEWUSER,
> .get = userns_get,
> .put = userns_put,
> .install = userns_install,
> + .owner = userns_owner,
> };
>
> static __init int user_namespaces_init(void)
> diff --git a/kernel/utsname.c b/kernel/utsname.c
> index f3b0bb4..0795e97 100644
> --- a/kernel/utsname.c
> +++ b/kernel/utsname.c
> @@ -154,10 +154,16 @@ static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
> return 0;
> }
>
> +static struct user_namespace *utsns_owner(struct ns_common *ns)
> +{
> + return to_uts_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations utsns_operations = {
> .name = "uts",
> .type = CLONE_NEWUTS,
> .get = utsns_get,
> .put = utsns_put,
> .install = utsns_install,
> + .owner = utsns_owner,
> };
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 3e2812a..8619e89 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -1016,11 +1016,17 @@ static int netns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> return 0;
> }
>
> +static struct user_namespace *netns_owner(struct ns_common *ns)
> +{
> + return to_net_ns(ns)->user_ns;
> +}
> +
> const struct proc_ns_operations netns_operations = {
> .name = "net",
> .type = CLONE_NEWNET,
> .get = netns_get,
> .put = netns_put,
> .install = netns_install,
> + .owner = netns_owner,
> };
> #endif
> --
> 2.5.5
>
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