---
license: cc-by-4.0
language:
  - en
pretty_name: Linux IOCTL Census (public structural tier)
tags:
  - linux-kernel
  - ioctl
  - attack-surface
  - security
  - static-analysis
  - census
configs:
  - config_name: binaries
    data_files: data/binaries.parquet
  - config_name: dispatchers
    data_files: data/dispatchers.parquet
  - config_name: ioctl_codes
    data_files: data/ioctl_codes.parquet
  - config_name: handlers
    data_files: data/handlers.parquet
  - config_name: gates
    data_files: data/gates.parquet
  - config_name: kb_meta
    data_files: data/kb_meta.parquet
---

# Linux IOCTL Census -- public structural tier

A source-derived census of the Linux kernel local ioctl/proc/sysfs handler
surface: for each registered handler, its decoded `_IOC` command table, the
permission gates on its path, and a capability-ungated reachability upper
bound. The schema is **identical to the Windows IOCTL Census**
(`mjbommar/ioctl-census`), so the two can be queried and compared together.

This is the **public structural tier**: everything derivable from the
already-public kernel source. The targeting tier (controlled-input sinks,
LLM triage, ranked unaudited surface) is intentionally withheld.

## Tables

| table | rows | what |
|---|---|---|
| `binaries` | 878 | one row per driver source file that registers a handler (module granularity) |
| `dispatchers` | 2914 | registered handler entries (`unlocked_ioctl`, `proc_write`, `store`, ...) |
| `ioctl_codes` | 1289 | decoded `_IOC` commands (dir/type/nr/size + arg struct + cmd symbol) |
| `handlers` | 2914 | handler functions (symbol + file:line) |
| `gates` | 1298 | capability / f_mode / field-check permission gates on handler paths |

`*_va` columns hold a stable 64-bit `hash(usr)` (a symbol id, not an address;
Linux is relocatable). The human location is in the companion `name`/`file`/
`line` columns with `loc_kind in {symbol, site}`. `imagebase = 0`.

## Provenance

- Source: in-tree Linux kernel source (kg snapshot; exact `git describe`
  recorded in `kb_meta`).
- Coverage: **169 in-tree subtrees, 878 modules** -- the whole source an
  `x86_64` `allmodconfig` build compiles (84% of source `.c` files; the
  uncompiled remainder is other-architecture platform code). A second build for `arm64` adds only 1 ioctl module and no new command codes.
- Determinism: the structural tables are content-hash byte-identical across
  two independent rebuilds (provenance timestamps excluded).
- Extraction: libclang over the kernel source (registrations, sinks, gates,
  reachability) + a `clang -E -dM` `_IOC` command-code resolver. Resolution
  rate 80% (1289 of 1614 switch-case symbols; the remainder are dominated by
  legacy non-`_IOC` numeric command constants that carry no decodable structure).

## Important caveats (read before using)

- **`user_reachable` is an UPPER BOUND**, not a proof of unprivileged
  reach: it means "no hard init-namespace capability gate on the handler
  path." Precise node DAC (device-node mode/owner via udev/devtmpfs) is
  resolved only for a curated subset; a `user_reachable=true` row may still
  be gated by a root/hardware-only device node.
- **Registration-type coverage**: handlers registered via `file_operations`/
  `proc_ops`/`block_device_operations`/sysfs attrs are captured. NOT yet
  captured: ops-table dispatch (DRM/V4L2/ALSA route per-command handlers
  through tables such as `drm_ioctl_desc`/`v4l2_ioctl_ops`, so for those
  subsystems only the fops-level dispatcher is recovered, not the per-command
  surface), tty line disciplines (`tty_ldisc_ops`), the core `blkdev_ioctl`
  switch, and netlink.
- Static analysis only; no runtime confirmation.

## Companion

Schema-compatible sibling: the Windows IOCTL Census
(`huggingface.co/datasets/mjbommar/ioctl-census`). See the paper *Toward a
Linux IOCTL Census* for method, validation, and the cross-OS comparison.

## License

CC-BY-4.0 (data). The census tooling is released separately under the
project's source license.