From 1b852bceb0d111e510d1a15826ecc4a19358d512 Mon Sep 17 00:00:00 2001 From: Eric W. Biederman Date: Fri, 8 May 2015 23:22:29 -0500 Subject: mnt: Refactor the logic for mounting sysfs and proc in a user namespace Fresh mounts of proc and sysfs are a very special case that works very much like a bind mount. Unfortunately the current structure can not preserve the MNT_LOCK... mount flags. Therefore refactor the logic into a form that can be modified to preserve those lock bits. Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount of the filesystem be fully visible in the current mount namespace, before the filesystem may be mounted. Move the logic for calling fs_fully_visible from proc and sysfs into fs/namespace.c where it has greater access to mount namespace state. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" --- fs/namespace.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index 1b9e11167bae..8e7edaf60fe1 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2332,6 +2332,8 @@ unlock: return err; } +static bool fs_fully_visible(struct file_system_type *fs_type); + /* * create a new mount for userspace and request it to be added into the * namespace's tree @@ -2363,6 +2365,10 @@ static int do_new_mount(struct path *path, const char *fstype, int flags, flags |= MS_NODEV; mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV; } + if (type->fs_flags & FS_USERNS_VISIBLE) { + if (!fs_fully_visible(type)) + return -EPERM; + } } mnt = vfs_kern_mount(type, flags, name, data); @@ -3164,7 +3170,7 @@ bool current_chrooted(void) return chrooted; } -bool fs_fully_visible(struct file_system_type *type) +static bool fs_fully_visible(struct file_system_type *type) { struct mnt_namespace *ns = current->nsproxy->mnt_ns; struct mount *mnt; -- cgit v1.2.3-55-g7522