1 files changed, 95 insertions, 26 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index ad8ea9bc2518..ef69fa5d2e5b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -831,6 +831,10 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 	if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
 		mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
 
+	/* Don't allow unprivileged users to reveal what is under a mount */
+	if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
+		mnt->mnt.mnt_flags |= MNT_LOCKED;
+
 	atomic_inc(&sb->s_active);
 	mnt->mnt.mnt_sb = sb;
 	mnt->mnt.mnt_root = dget(root);
@@ -1327,6 +1331,8 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
 		goto dput_and_out;
 	if (!check_mnt(mnt))
 		goto dput_and_out;
+	if (mnt->mnt.mnt_flags & MNT_LOCKED)
+		goto dput_and_out;
 
 	retval = do_umount(mnt, flags);
 dput_and_out:
@@ -1349,14 +1355,11 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
 
 #endif
 
-static bool mnt_ns_loop(struct path *path)
+static bool is_mnt_ns_file(struct dentry *dentry)
 {
-	/* Could bind mounting the mount namespace inode cause a
-	 * mount namespace loop?
-	 */
-	struct inode *inode = path->dentry->d_inode;
+	/* Is this a proxy for a mount namespace? */
+	struct inode *inode = dentry->d_inode;
 	struct proc_ns *ei;
-	struct mnt_namespace *mnt_ns;
 
 	if (!proc_ns_inode(inode))
 		return false;
@@ -1365,7 +1368,19 @@ static bool mnt_ns_loop(struct path *path)
 	if (ei->ns_ops != &mntns_operations)
 		return false;
 
-	mnt_ns = ei->ns;
+	return true;
+}
+
+static bool mnt_ns_loop(struct dentry *dentry)
+{
+	/* Could bind mounting the mount namespace inode cause a
+	 * mount namespace loop?
+	 */
+	struct mnt_namespace *mnt_ns;
+	if (!is_mnt_ns_file(dentry))
+		return false;
+
+	mnt_ns = get_proc_ns(dentry->d_inode)->ns;
 	return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
 }
 
@@ -1374,13 +1389,17 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
 {
 	struct mount *res, *p, *q, *r, *parent;
 
-	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
+	if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
+		return ERR_PTR(-EINVAL);
+
+	if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
 		return ERR_PTR(-EINVAL);
 
 	res = q = clone_mnt(mnt, dentry, flag);
 	if (IS_ERR(q))
 		return q;
 
+	q->mnt.mnt_flags &= ~MNT_LOCKED;
 	q->mnt_mountpoint = mnt->mnt_mountpoint;
 
 	p = mnt;
@@ -1390,7 +1409,13 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
 			continue;
 
 		for (s = r; s; s = next_mnt(s, r)) {
-			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
+			if (!(flag & CL_COPY_UNBINDABLE) &&
+			    IS_MNT_UNBINDABLE(s)) {
+				s = skip_mnt_tree(s);
+				continue;
+			}
+			if (!(flag & CL_COPY_MNT_NS_FILE) &&
+			    is_mnt_ns_file(s->mnt.mnt_root)) {
 				s = skip_mnt_tree(s);
 				continue;
 			}
@@ -1696,6 +1721,19 @@ static int do_change_type(struct path *path, int flag)
 	return err;
 }
 
+static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
+{
+	struct mount *child;
+	list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
+		if (!is_subdir(child->mnt_mountpoint, dentry))
+			continue;
+
+		if (child->mnt.mnt_flags & MNT_LOCKED)
+			return true;
+	}
+	return false;
+}
+
 /*
  * do loopback mount.
  */
@@ -1713,7 +1751,7 @@ static int do_loopback(struct path *path, const char *old_name,
 		return err;
 
 	err = -EINVAL;
-	if (mnt_ns_loop(&old_path))
+	if (mnt_ns_loop(old_path.dentry))
 		goto out; 
 
 	mp = lock_mount(path);
@@ -1731,8 +1769,11 @@ static int do_loopback(struct path *path, const char *old_name,
 	if (!check_mnt(parent) || !check_mnt(old))
 		goto out2;
 
+	if (!recurse && has_locked_children(old, old_path.dentry))
+		goto out2;
+
 	if (recurse)
-		mnt = copy_tree(old, old_path.dentry, 0);
+		mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
 	else
 		mnt = clone_mnt(old, old_path.dentry, 0);
 
@@ -1741,6 +1782,8 @@ static int do_loopback(struct path *path, const char *old_name,
 		goto out2;
 	}
 
+	mnt->mnt.mnt_flags &= ~MNT_LOCKED;
+
 	err = graft_tree(mnt, parent, mp);
 	if (err) {
 		br_write_lock(&vfsmount_lock);
@@ -1853,6 +1896,9 @@ static int do_move_mount(struct path *path, const char *old_name)
 	if (!check_mnt(p) || !check_mnt(old))
 		goto out1;
 
+	if (old->mnt.mnt_flags & MNT_LOCKED)
+		goto out1;
+
 	err = -EINVAL;
 	if (old_path.dentry != old_path.mnt->mnt_root)
 		goto out1;
@@ -2389,7 +2435,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
 
 	namespace_lock();
 	/* First pass: copy the tree topology */
-	copy_flags = CL_COPY_ALL | CL_EXPIRE;
+	copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
 	if (user_ns != mnt_ns->user_ns)
 		copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
 	new = copy_tree(old, old->mnt.mnt_root, copy_flags);
@@ -2424,6 +2470,10 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
 		}
 		p = next_mnt(p, old);
 		q = next_mnt(q, new);
+		if (!q)
+			break;
+		while (p->mnt.mnt_root != q->mnt.mnt_root)
+			p = next_mnt(p, old);
 	}
 	namespace_unlock();
 
@@ -2630,6 +2680,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
 		goto out4;
 	if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
 		goto out4;
+	if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
+		goto out4;
 	error = -ENOENT;
 	if (d_unlinked(new.dentry))
 		goto out4;
@@ -2653,6 +2705,10 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
 	br_write_lock(&vfsmount_lock);
 	detach_mnt(new_mnt, &parent_path);
 	detach_mnt(root_mnt, &root_parent);
+	if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
+		new_mnt->mnt.mnt_flags |= MNT_LOCKED;
+		root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
+	}
 	/* mount old root on put_old */
 	attach_mnt(root_mnt, old_mnt, old_mp);
 	/* mount new_root on / */
@@ -2811,25 +2867,38 @@ bool current_chrooted(void)
 	return chrooted;
 }
 
-void update_mnt_policy(struct user_namespace *userns)
+bool fs_fully_visible(struct file_system_type *type)
 {
 	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
 	struct mount *mnt;
+	bool visible = false;
 
-	down_read(&namespace_sem);
+	if (unlikely(!ns))
+		return false;
+
+	namespace_lock();
 	list_for_each_entry(mnt, &ns->list, mnt_list) {
-		switch (mnt->mnt.mnt_sb->s_magic) {
-		case SYSFS_MAGIC:
-			userns->may_mount_sysfs = true;
-			break;
-		case PROC_SUPER_MAGIC:
-			userns->may_mount_proc = true;
-			break;
+		struct mount *child;
+		if (mnt->mnt.mnt_sb->s_type != type)
+			continue;
+
+		/* This mount is not fully visible if there are any child mounts
+		 * that cover anything except for empty directories.
+		 */
+		list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
+			struct inode *inode = child->mnt_mountpoint->d_inode;
+			if (!S_ISDIR(inode->i_mode))
+				goto next;
+			if (inode->i_nlink != 2)
+				goto next;
 		}
-		if (userns->may_mount_sysfs && userns->may_mount_proc)
-			break;
+		visible = true;
+		goto found;
+	next:	;
 	}
-	up_read(&namespace_sem);
+found:
+	namespace_unlock();
+	return visible;
 }
 
 static void *mntns_get(struct task_struct *task)
@@ -2860,8 +2929,8 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns)
 	struct path root;
 
 	if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
-	    !nsown_capable(CAP_SYS_CHROOT) ||
-	    !nsown_capable(CAP_SYS_ADMIN))
+	    !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
+	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 		return -EPERM;
 
 	if (fs->users != 1)