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Paul Chaignon 2ba199067b selftests/bpf: Cover invariant violation case from syzbot
This patch adds a selftest for the change in the previous patch. The
selftest is derived from a syzbot reproducer from [1] (among the 22
reproducers on that page, only 4 still reproduced on latest bpf tree,
all being small variants of the same invariant violation).

The test case failure without the previous patch is shown below.

  0: R1=ctx() R10=fp0
  0: (85) call bpf_get_prandom_u32#7    ; R0=scalar()
  1: (bf) r5 = r0                       ; R0=scalar(id=1) R5=scalar(id=1)
  2: (57) r5 &= -4                      ; R5=scalar(smax=0x7ffffffffffffffc,umax=0xfffffffffffffffc,smax32=0x7ffffffc,umax32=0xfffffffc,var_off=(0x0; 0xfffffffffffffffc))
  3: (bf) r7 = r0                       ; R0=scalar(id=1) R7=scalar(id=1)
  4: (57) r7 &= 1                       ; R7=scalar(smin=smin32=0,smax=umax=smax32=umax32=1,var_off=(0x0; 0x1))
  5: (07) r7 += -43                     ; R7=scalar(smin=smin32=-43,smax=smax32=-42,umin=0xffffffffffffffd5,umax=0xffffffffffffffd6,umin32=0xffffffd5,umax32=0xffffffd6,var_off=(0xffffffffffffffd4; 0x3))
  6: (5e) if w5 != w7 goto pc+1
  verifier bug: REG INVARIANTS VIOLATION (false_reg1): range bounds violation u64=[0xffffffd5, 0xffffffffffffffd4] s64=[0x80000000ffffffd5, 0x7fffffffffffffd4] u32=[0xffffffd5, 0xffffffd4] s32=[0xffffffd5, 0xffffffd4] var_off=(0xffffffd4, 0xffffffff00000000)

R5 and R7 are prepared such that their tnums intersection results in a
known constant but that constant isn't within R7's u32 bounds.
is_branch_taken isn't able to detect this case today, so the verifier
walks the impossible fallthrough branch. After regs_refine_cond_op and
reg_bounds_sync refine R5 on the assumption that the branch is taken,
the impossibility becomes apparent and results in an invariant violation
for R5: umin32 is greater than umax32.

The previous patch fixes this by using regs_refine_cond_op and
reg_bounds_sync in is_branch_taken to detect the impossible branch. The
fallthrough branch is therefore correctly detected as dead code.

Link: https://syzkaller.appspot.com/bug?extid=c950cc277150935cc0b5 [1]
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/b1e22233a3206ead522f02eda27b9c5c991a0de9.1775142354.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2026-04-02 18:23:25 -07:00
arch bpf,arc_jit: Fix missing newline in pr_err messages 2026-03-29 09:59:00 -07:00
block block-7.0-20260305 2026-03-06 08:36:18 -08:00
certs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
crypto crypto: testmgr - Fix stale references to aes-generic 2026-03-03 11:57:15 -08:00
Documentation Driver core fixes for 7.0-rc5 2026-03-21 16:59:09 -07:00
drivers Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 7.0-rc5 2026-03-22 19:33:29 -07:00
fs for-7.0-rc4-tag 2026-03-21 08:42:17 -07:00
include bpf: Use bpf_verifier_env buffers for reg_set_min_max 2026-04-02 18:23:25 -07:00
init io_uring-7.0-20260305 2026-03-06 08:31:36 -08:00
io_uring io_uring-7.0-20260320 2026-03-20 09:58:56 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel bpf: Simulate branches to prune based on range violations 2026-04-02 18:23:25 -07:00
lib Bootconfig fixes for v7.0-rc4 2026-03-21 08:46:13 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm 6 hotfixes. 4 are cc:stable. 3 are for MM. 2026-03-16 12:21:00 -07:00
net selftests/bpf: Add trampolines single and multi-level pointer params test coverage 2026-03-24 13:36:32 -07:00
rust Rust fixes for v7.0 (2nd) 2026-03-14 12:35:16 -07:00
samples drm-fixes for 7.0-rc4 2026-03-13 15:38:55 -07:00
scripts kbuild, bpf: Specify "layout" optional feature 2026-03-26 13:53:57 -07:00
security apparmor: fix race between freeing data and fs accessing it 2026-03-09 16:05:44 -07:00
sound driver core: platform: use generic driver_override infrastructure 2026-03-17 20:30:57 +01:00
tools selftests/bpf: Cover invariant violation case from syzbot 2026-04-02 18:23:25 -07:00
usr kbuild: uapi: drop dependency on CC_CAN_LINK 2026-01-16 15:02:11 -07:00
virt KVM generic changes for 7.0 2026-03-11 18:01:55 +01:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.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: add rst extension 2026-01-26 19:07:09 -08:00
.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 rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap MAINTAINERS: update email address for Ignat Korchagin 2026-03-10 16:01:49 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.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 MAINTAINERS: remove Thomas Falcon from IBM ibmvnic 2026-03-05 07:35:45 -08:00
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 bpf: Update MAINTAINERS file for general BPF entry 2026-03-24 09:05:11 -07:00
Makefile Linux 7.0-rc5 2026-03-22 14:42:17 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

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

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst