lkml.org 
[lkml]   [2015]   [Jul]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.1 08/65] mnt: Refactor the logic for mounting sysfs and proc in a user namespace
Date
4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xmission.com>

commit 1b852bceb0d111e510d1a15826ecc4a19358d512 upstream.

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.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/namespace.c | 8 +++++++-
fs/proc/root.c | 5 +----
fs/sysfs/mount.c | 5 +----
include/linux/fs.h | 2 +-
4 files changed, 10 insertions(+), 10 deletions(-)

--- 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 *pat
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;
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -112,9 +112,6 @@ static struct dentry *proc_mount(struct
ns = task_active_pid_ns(current);
options = data;

- if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
- return ERR_PTR(-EPERM);
-
/* Does the mounter have privilege over the pid namespace? */
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
@@ -159,7 +156,7 @@ static struct file_system_type proc_fs_t
.name = "proc",
.mount = proc_mount,
.kill_sb = proc_kill_sb,
- .fs_flags = FS_USERNS_MOUNT,
+ .fs_flags = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
};

void __init proc_root_init(void)
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -31,9 +31,6 @@ static struct dentry *sysfs_mount(struct
bool new_sb;

if (!(flags & MS_KERNMOUNT)) {
- if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
- return ERR_PTR(-EPERM);
-
if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
return ERR_PTR(-EPERM);
}
@@ -58,7 +55,7 @@ static struct file_system_type sysfs_fs_
.name = "sysfs",
.mount = sysfs_mount,
.kill_sb = sysfs_kill_sb,
- .fs_flags = FS_USERNS_MOUNT,
+ .fs_flags = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
};

int __init sysfs_init(void)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1897,6 +1897,7 @@ struct file_system_type {
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
+#define FS_USERNS_VISIBLE 32 /* FS must already be visible */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);
@@ -1984,7 +1985,6 @@ extern int vfs_ustat(dev_t, struct kstat
extern int freeze_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
extern bool our_mnt(struct vfsmount *mnt);
-extern bool fs_fully_visible(struct file_system_type *);

extern int current_umask(void);




\
 
 \ /
  Last update: 2015-07-19 22:01    [W:0.151 / U:0.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site