1 files changed, 87 insertions, 13 deletions

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 8f20d6016e20..fb7b397a1297 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -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 +92,94 @@ 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);
+                mntput(mnt);
                 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;
+}
+
+static 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 *relative;
+
+                relative = get_ns(ns);
+                if (IS_ERR(relative)) {
+                        put_unused_fd(fd);
+                        return PTR_ERR(relative);
+                }
+
+                err = __ns_get_path(&path, relative);
+                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);
+        case NS_GET_PARENT:
+                if (!ns->ops->get_parent)
+                        return -EINVAL;
+                return open_related_ns(ns, ns->ops->get_parent);
+        default:
+                return -ENOTTY;
+        }
+}
+
 int ns_get_name(char *buf, size_t size, struct task_struct *task,
                         const struct proc_ns_operations *ns_ops)
 {