lkml.org 
[lkml]   [2013]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH review 4/6] userns: Allow the userns root to mount of devpts

    - The context in which devpts is mounted has no effect on the creation
    of ptys as the /dev/ptmx interface has been used by unprivileged
    users for many years.

    - Only support unprivileged mounts in combination with the newinstance
    option to ensure that mounting of /dev/pts in a user namespace will
    not allow the options of an existing mount of devpts to be modified.

    - Create /dev/pts/ptmx as the root user in the user namespace that
    mounts devpts so that it's permissions to be changed.

    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    ---
    fs/devpts/inode.c | 18 ++++++++++++++++++
    1 files changed, 18 insertions(+), 0 deletions(-)

    diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
    index 472e6be..073d30b 100644
    --- a/fs/devpts/inode.c
    +++ b/fs/devpts/inode.c
    @@ -243,6 +243,13 @@ static int mknod_ptmx(struct super_block *sb)
    struct dentry *root = sb->s_root;
    struct pts_fs_info *fsi = DEVPTS_SB(sb);
    struct pts_mount_opts *opts = &fsi->mount_opts;
    + kuid_t root_uid;
    + kgid_t root_gid;
    +
    + root_uid = make_kuid(current_user_ns(), 0);
    + root_gid = make_kgid(current_user_ns(), 0);
    + if (!uid_valid(root_uid) || !gid_valid(root_gid))
    + return -EINVAL;

    mutex_lock(&root->d_inode->i_mutex);

    @@ -273,6 +280,8 @@ static int mknod_ptmx(struct super_block *sb)

    mode = S_IFCHR|opts->ptmxmode;
    init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
    + inode->i_uid = root_uid;
    + inode->i_gid = root_gid;

    d_add(dentry, inode);

    @@ -438,6 +447,12 @@ static struct dentry *devpts_mount(struct file_system_type *fs_type,
    if (error)
    return ERR_PTR(error);

    + /* Require newinstance for all user namespace mounts to ensure
    + * the mount options are not changed.
    + */
    + if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
    + return ERR_PTR(-EINVAL);
    +
    if (opts.newinstance)
    s = sget(fs_type, NULL, set_anon_super, flags, NULL);
    else
    @@ -491,6 +506,9 @@ static struct file_system_type devpts_fs_type = {
    .name = "devpts",
    .mount = devpts_mount,
    .kill_sb = devpts_kill_sb,
    +#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
    + .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT,
    +#endif
    };

    /*
    --
    1.7.5.4


    \
     
     \ /
      Last update: 2013-01-26 04:01    [W:0.026 / U:118.116 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site