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Abhinav Saxena 7553f5173e selftests/tty: add TIOCSTI test suite 
TIOCSTI is a TTY ioctl command that allows inserting characters into
the terminal input queue, making it appear as if the user typed those
characters. This functionality has behavior that varies based on system
configuration and process credentials.

The dev.tty.legacy_tiocsti sysctl introduced in commit 83efeeeb3d
("tty: Allow TIOCSTI to be disabled") controls TIOCSTI usage. When
disabled, TIOCSTI requires CAP_SYS_ADMIN capability.

The current implementation checks the current process's credentials via
capable(CAP_SYS_ADMIN), but does not validate against the file opener's
credentials stored in file->f_cred. This creates different behavior when
file descriptors are passed between processes via SCM_RIGHTS.

Add a test suite with 16 test variants using fixture variants to verify
TIOCSTI behavior when dev.tty.legacy_tiocsti is enabled/disabled:

- Basic TIOCSTI tests (8 variants): Direct testing with different
  capability and controlling terminal combinations
- FD passing tests (8 variants): Test behavior when file descriptors
  are passed between processes with different capabilities

The FD passing tests document this behavior - some tests show different
results than expected based on file opener credentials, demonstrating
that TIOCSTI uses current process credentials rather than file opener
credentials.

The tests validate proper enforcement of the legacy_tiocsti sysctl. Test
implementation uses openpty(3) with TIOCSCTTY for isolated PTY
environments. See tty_ioctl(4) for details on TIOCSTI behavior and
security requirements.

Signed-off-by: Abhinav Saxena <xandfury@gmail.com>
Link: https://patch.msgid.link/20250903-toicsti-bug-v4-1-4894b6649ef8@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-22 12:09:07 +02:00
arch - Reset the why-the-system-rebooted register on AMD to avoid stale bits 2025-10-19 04:41:27 -10:00
block block-6.18-20251016 2025-10-17 08:31:26 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation dt-bindings: serial: samsung: add samsung,exynos8890-uart compatible 2025-10-22 12:04:33 +02:00
drivers serial: 8250_pcilib: Replace deprecated PCI functions 2025-10-22 12:06:53 +02:00
fs Description for this pull request: 2025-10-18 07:23:59 -10:00
include hid-for-linus-2025101701 2025-10-18 08:18:18 -10:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/rw: check for NULL io_br_sel when putting a buffer 2025-10-15 13:38:53 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel - Make sure the check for lost pelt idle time is done unconditionally to 2025-10-19 04:59:43 -10:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab: reset slab->obj_ext when freeing and it is OBJEXTS_ALLOC_FAIL 2025-10-16 15:16:45 +02:00
net bpf-fixes 2025-10-18 08:00:43 -10:00
rust rust: bitmap: fix formatting 2025-10-17 13:02:22 +02:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound ALSA: hda/realtek: Fix mute led for HP Omen 17-cb0xxx 2025-10-17 16:37:21 +02:00
tools selftests/tty: add TIOCSTI test suite 2025-10-22 12:09:07 +02:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM x86 fixes for 6.18: 2025-10-18 10:25:43 +02:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap Including fixes from CAN 2025-10-16 09:41:21 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Including fixes from CAN 2025-10-16 09:41:21 -07:00
Makefile Linux 6.18-rc2 2025-10-19 15:19:16 -10:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.