diff options
author | Eric W. Biederman <ebiederm@xmission.com> | 2012-08-21 04:28:58 +0400 |
---|---|---|
committer | Eric W. Biederman <ebiederm@xmission.com> | 2013-01-27 10:22:21 +0400 |
commit | ec2aa8e8dd7d35524a68c89b9e7ceb07fb002561 (patch) | |
tree | e6dccae5db69231b9f7c4bd362bed2031de7516a | |
parent | e11f0ae388f227d7ad03953e19034dec55286650 (diff) | |
download | linux-ec2aa8e8dd7d35524a68c89b9e7ceb07fb002561.tar.xz |
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.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r-- | 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 472e6befc54d..073d30b9d1ac 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 }; /* |