@@ -5,11 +5,16 @@
#include <linux/magic.h>
#include <linux/ktime.h>
#include <linux/seq_file.h>
+#include <linux/user_namespace.h>
+#include <linux/nsfs.h>
static struct vfsmount *nsfs_mnt;
+static long ns_ioctl(struct file *filp, unsigned int ioctl,
+ unsigned long arg);
static const struct file_operations ns_file_operations = {
.llseek = no_llseek,
+ .unlocked_ioctl = ns_ioctl,
};
static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
@@ -44,22 +49,14 @@ static void nsfs_evict(struct inode *inode)
ns->ops->put(ns);
}
-void *ns_get_path(struct path *path, struct task_struct *task,
- const struct proc_ns_operations *ns_ops)
+static void *__ns_get_path(struct path *path, struct ns_common *ns)
{
struct vfsmount *mnt = mntget(nsfs_mnt);
struct qstr qname = { .name = "", };
struct dentry *dentry;
struct inode *inode;
- struct ns_common *ns;
unsigned long d;
-again:
- ns = ns_ops->get(task);
- if (!ns) {
- mntput(mnt);
- return ERR_PTR(-ENOENT);
- }
rcu_read_lock();
d = atomic_long_read(&ns->stashed);
if (!d)
@@ -68,7 +65,7 @@ again:
if (!lockref_get_not_dead(&dentry->d_lockref))
goto slow;
rcu_read_unlock();
- ns_ops->put(ns);
+ ns->ops->put(ns);
got_it:
path->mnt = mnt;
path->dentry = dentry;
@@ -77,7 +74,7 @@ slow:
rcu_read_unlock();
inode = new_inode_pseudo(mnt->mnt_sb);
if (!inode) {
- ns_ops->put(ns);
+ ns->ops->put(ns);
mntput(mnt);
return ERR_PTR(-ENOMEM);
}
@@ -95,17 +92,88 @@ slow:
return ERR_PTR(-ENOMEM);
}
d_instantiate(dentry, inode);
- dentry->d_fsdata = (void *)ns_ops;
+ dentry->d_fsdata = (void *)ns->ops;
d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
if (d) {
d_delete(dentry); /* make sure ->d_prune() does nothing */
dput(dentry);
cpu_relax();
- goto again;
+ return ERR_PTR(-EAGAIN);
}
goto got_it;
}
+void *ns_get_path(struct path *path, struct task_struct *task,
+ const struct proc_ns_operations *ns_ops)
+{
+ struct ns_common *ns;
+ void *ret;
+
+again:
+ ns = ns_ops->get(task);
+ if (!ns)
+ return ERR_PTR(-ENOENT);
+
+ ret = __ns_get_path(path, ns);
+ if (IS_ERR(ret) && PTR_ERR(ret) == -EAGAIN)
+ goto again;
+ return ret;
+}
+
+int open_related_ns(struct ns_common *ns,
+ struct ns_common *(*get_ns)(struct ns_common *ns))
+{
+ struct path path = {};
+ struct file *f;
+ void *err;
+ int fd;
+
+ fd = get_unused_fd_flags(O_CLOEXEC);
+ if (fd < 0)
+ return fd;
+
+ while (1) {
+ struct ns_common *parent;
+
+ parent = get_ns(ns);
+ if (IS_ERR(parent)) {
+ put_unused_fd(fd);
+ return PTR_ERR(parent);
+ }
+
+ err = __ns_get_path(&path, parent);
+ if (IS_ERR(err) && PTR_ERR(err) == -EAGAIN)
+ continue;
+ break;
+ }
+ if (IS_ERR(err)) {
+ put_unused_fd(fd);
+ return PTR_ERR(err);
+ }
+
+ f = dentry_open(&path, O_RDONLY, current_cred());
+ path_put(&path);
+ if (IS_ERR(f)) {
+ put_unused_fd(fd);
+ fd = PTR_ERR(f);
+ } else
+ fd_install(fd, f);
+ return fd;
+}
+
+static long ns_ioctl(struct file *filp, unsigned int ioctl,
+ unsigned long arg)
+{
+ struct ns_common *ns = get_proc_ns(file_inode(filp));
+
+ switch (ioctl) {
+ case NS_GET_USERNS:
+ return open_related_ns(ns, ns_get_owner);
+ default:
+ return -ENOTTY;
+ }
+}
+
int ns_get_name(char *buf, size_t size, struct task_struct *task,
const struct proc_ns_operations *ns_ops)
{
new file mode 100644
@@ -0,0 +1,9 @@
+#ifndef __LINUX_NSFS_H
+#define __LINUX_NSFS_H
+
+#include <linux/ioctl.h>
+
+#define NSIO 0xb7
+#define NS_GET_USERNS _IO(NSIO, 0x1)
+
+#endif /* __LINUX_NSFS_H */
Each namespace has an owning user namespace and now there is not way to discover these relationships. Understending namespaces relationships allows to answer the question: what capability does process X have to perform operations on a resource governed by namespace Y? After a long discussion, Eric W. Biederman proposed to use ioctl-s for this purpose. The NS_GET_USERNS ioctl returns a file descriptor to an owning user namespace. It returns EPERM if a target namespace is outside of a current user namespace. Link: https://lkml.org/lkml/2016/7/6/158 Signed-off-by: Andrey Vagin <avagin@openvz.org> --- fs/nsfs.c | 94 ++++++++++++++++++++++++++++++++++++++++------- include/uapi/linux/nsfs.h | 9 +++++ 2 files changed, 90 insertions(+), 13 deletions(-) create mode 100644 include/uapi/linux/nsfs.h