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Breno Leitao dd0dcfe8ef mm: kmemleak: default min_unref_scans to 2 for verbose auto-scan
Patch series "mm: kmemleak: default min_unref_scans to 2 for verbose
kernels", v2.

When CONFIG_DEBUG_KMEMLEAK_VERBOSE is set, which means the host is in
auto scan mode, set min_unref_scans to 2, avoiding false positives.

CONFIG_DEBUG_KMEMLEAK_VERBOSE depends on CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN,
so a kernel built with it already runs the scan thread periodically and
the user has asked for detailed leak reports.

The confirming second scan comes for free there, so default
min_unref_scans to 2 in that case and keep it at 1 everywhere else.
CONFIG_DEBUG_KMEMLEAK_VERBOSE defaults to n, so nothing changes for
kernels that do not opt in.

The other two patches bring the documentation and the selftest comments
in line with the new conditional default.

PS: A similar patch (v1 of this patchset) is applied to Meta's kernel,
in real production hosts.


This patch (of 3):

min_unref_scans defers reporting an object as leaked until it has stayed
unreferenced for that many consecutive scans, filtering out objects that
are only transiently unreferenced during a scan.

It defaults to 1, which reports on the first unreferenced scan.

CONFIG_DEBUG_KMEMLEAK_VERBOSE depends on CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN,
so a kernel built with it runs the scan thread periodically and the user
has opted into detailed leak reporting.  A second confirming scan then
happens on its own.

Default min_unref_scans to 2 there to suppress transient false positives,
and keep it at 1 otherwise, where a manually triggered scan is expected to
report immediately.  The value stays writable through the module
parameter.

CONFIG_DEBUG_KMEMLEAK_VERBOSE defaults to n, so this does not change the
default for kernels that do not opt in.

Link: https://lore.kernel.org/20260731-kmemleak_hardened-v2-0-7b9689ac77cb@debian.org
Link: https://lore.kernel.org/20260731-kmemleak_hardened-v2-1-7b9689ac77cb@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-08-24 18:43:18 -07:00
arch mm: provide vma_[flags_]is_cow_mapping() and remove is_cow_mapping() 2026-08-24 18:42:50 -07:00
block block: fix aligning of bounced dio read bios 2026-07-16 06:11:37 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto crypto: aes - Fix conditions for selecting MAC dependencies 2026-07-09 11:06:22 -04:00
Documentation mm: kmemleak: report leaks only after N consecutive unreferenced scans 2026-08-24 18:43:17 -07:00
drivers shmem: provide a shmem_write_folio wrapper 2026-08-24 18:43:14 -07:00
fs mm/swap: remove SWP_FS_OPS 2026-08-24 18:43:15 -07:00
include mm/vmstat: add NRSWP{IN,OUT} counters 2026-08-24 18:43:15 -07:00
init mm/mseal: fix mseal documentation for 32-bit kernels 2026-08-06 18:57:12 -07:00
io_uring io_uring-7.2-20260724 2026-07-24 19:58:03 -07:00
ipc mm/vma: update do_mmap() to use vma_flags_t 2026-08-06 18:57:01 -07:00
kernel mm: provide vma_[flags_]is_cow_mapping() and remove is_cow_mapping() 2026-08-24 18:42:50 -07:00
lib alloc_tag: add ioctl to /proc/allocinfo 2026-08-24 18:43:12 -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 mm: kmemleak: default min_unref_scans to 2 for verbose auto-scan 2026-08-24 18:43:18 -07:00
net BPF fixes: 2026-07-24 19:31:12 -07:00
rust rust: time: fix as_micros_ceil() to round correctly for negative Delta 2026-07-18 19:07:35 +02:00
samples Merge branch 'mm-hotfixes-stable' into mm-stable to pick up 2026-08-24 18:40:27 -07:00
scripts mm/page_owner: add MR_NEVER to enum migrate_reason and use it for last_migrate_reason 2026-07-28 21:11:50 -07:00
security keys: make keyring key-chunk byte order agree with keyring_diff_objects() 2026-07-23 18:23:39 +03:00
sound mm: introduce vma_get_page_prot() and use it 2026-08-06 18:57:03 -07:00
tools selftests: mm: test kmemleak's N-consecutive-scan leak confirmation 2026-08-24 18:43:18 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt mm: use linear_page_[index, delta]() consistently 2026-08-04 19:19:01 -07:00
.clang-format clang-format: fix formatting of guard() and scoped_guard() statements 2026-05-28 21:24:41 -07:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap mailmap: add entries for Guodong Xu 2026-08-13 18:06:47 -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
CREDITS MAINTAINERS: move inactive maintainer to CREDITS 2026-07-28 21:12:03 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS kselftest: alloc_tag: add kselftest for ioctl interface 2026-08-24 18:43:13 -07:00
Makefile Linux 7.2-rc5 2026-07-26 14:45:48 -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