/* * devpts_mount() * * If the '-o newinstance' mount option was specified, mount a new * (private) instance of devpts. PTYs created in this instance are * independent of the PTYs in other devpts instances. * * If the '-o newinstance' option was not specified, mount/remount the * initial kernel mount of devpts. This type of mount gives the * legacy, single-instance semantics. * * The 'newinstance' option is needed to support multiple namespace * semantics in devpts while preserving backward compatibility of the * current 'single-namespace' semantics. i.e all mounts of devpts * without the 'newinstance' mount option should bind to the initial * kernel mount, like mount_single(). * * Mounts with 'newinstance' option create a new, private namespace. * * NOTE: * * For single-mount semantics, devpts cannot use mount_single(), * because mount_single()/sget() find and use the super-block from * the most recent mount of devpts. But that recent mount may be a * 'newinstance' mount and mount_single() would pick the newinstance * super-block instead of the initial super-block. */ static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { int error; struct pts_mount_opts opts; struct super_block *s; error = parse_mount_options(data, PARSE_MOUNT, &opts); 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 s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags, NULL); if (IS_ERR(s)) return ERR_CAST(s); if (!s->s_root) { error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) goto out_undo_sget; s->s_flags |= MS_ACTIVE; } memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); error = mknod_ptmx(s); if (error) goto out_undo_sget; return dget(s->s_root); out_undo_sget: deactivate_locked_super(s); return ERR_PTR(error); }
/* * devpts_get_sb() * * If the '-o newinstance' mount option was specified, mount a new * (private) instance of devpts. PTYs created in this instance are * independent of the PTYs in other devpts instances. * * If the '-o newinstance' option was not specified, mount/remount the * initial kernel mount of devpts. This type of mount gives the * legacy, single-instance semantics. * * The 'newinstance' option is needed to support multiple namespace * semantics in devpts while preserving backward compatibility of the * current 'single-namespace' semantics. i.e all mounts of devpts * without the 'newinstance' mount option should bind to the initial * kernel mount, like get_sb_single(). * * Mounts with 'newinstance' option create a new, private namespace. * * NOTE: * * For single-mount semantics, devpts cannot use get_sb_single(), * because get_sb_single()/sget() find and use the super-block from * the most recent mount of devpts. But that recent mount may be a * 'newinstance' mount and get_sb_single() would pick the newinstance * super-block instead of the initial super-block. */ static int devpts_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { int error; struct pts_mount_opts opts; struct super_block *s; error = parse_mount_options(data, PARSE_MOUNT, &opts); if (error) return error; if (opts.newinstance) s = sget(fs_type, NULL, set_anon_super, NULL); else s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL); if (IS_ERR(s)) return PTR_ERR(s); if (!s->s_root) { s->s_flags = flags; error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) goto out_undo_sget; s->s_flags |= MS_ACTIVE; } simple_set_mnt(mnt, s); memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); error = mknod_ptmx(s); if (error) goto out_dput; return 0; out_dput: dput(s->s_root); /* undo dget() in simple_set_mnt() */ out_undo_sget: deactivate_locked_super(s); return error; }