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Hajime Tazaki 644ad84870 mm: nommu: point to the write iterator upon split_vma
When a user invokes munmap(2) on a partial region allocated by mmap(), the
kernel may split the original region if necessary and shrink it to the
correct size.  At the beginning of vmi_shrink_vma(), the unused part is
cleared; however, an assertion is triggered if the shrink occurs after
split_vma().

This commit fixes the issue by correctly configuring the pointer to the
iterator at the end of split_vma().

This bug was detected using the Linux Test Project (LTP) test linked
below, running on a nommu UML (User-Mode Linux) environment (via an
out-of-tree extension to UML).

Here is a minimal reproducible chunk of code for this issue:

	void *addr;
	size_t pagesize = getpagesize();

	addr = mmap(NULL, pagesize * 4, PROT_READ | PROT_WRITE,
		    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	munmap(addr + pagesize * 1, pagesize);

This is the console output with CONFIG_DEBUG_MAPLE_TREE=y.

nommu: WARN at __mas_set_range:791 (1)
MAS: tree=0000000091c23b08 enode=0000000065057663
(ma_active)
Store Type:
node_store
[9/9] index=70af8000 last=ffffffffffffffff
     min=0 max=ffffffffffffffff sheaf=0000000000000000, request 0
depth=0, flags=0
maple_tree(0000000091c23b08) flags 307, height 1 root 0000000083394c06
0-ffffffffffffffff: node 0000000010c90bd6 depth 0 type 1 parent
0000000050e1ddf8 contents: 0000000000000000 707A
7FFF 00000000eb0ac2b5 707AFFFF 0000000000000000 7093FFFF
0000000045ead616 7095FFFF 0000000000000000 7096CFFF 000
00000681c7151 7096FFFF 0000000000000000 70AF3FFF 000000006c78b9e9
70AF4FFF 000000001914ab0b 70AF7FFF 00000000000
00000 FFFFFFFFFFFFFFFF 0000000000000000 0 0000000000000000 0
0000000000000000 0 0000000000000000 0 0000000000000
000 0 00000000bca8be4f
  0-707a7fff: 0000000000000000
  707a8000-707affff: 00000000eb0ac2b5
  707b0000-7093ffff: 0000000000000000
  70940000-7095ffff: 0000000045ead616
  70960000-7096cfff: 0000000000000000
  7096d000-7096ffff: 00000000681c7151
  70970000-70af3fff: 0000000000000000
  70af4000-70af4fff: 000000006c78b9e9
  70af5000-70af7fff: 000000001914ab0b
  70af8000-ffffffffffffffff: 0000000000000000
nommu: Pass: 796 Run:797

Link: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/mseal/mseal02.c
Link: https://lore.kernel.org/20260702012546.665383-1-thehajime@gmail.com
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
History 2026-08-24 18:42:48 -07:00
arch Merge branch 'mm-hotfixes-stable' into mm-stable to pick up 2026-08-24 18:40:27 -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 Documentation: zram: remove sections numbering 2026-08-06 18:57:26 -07:00
drivers zram: use a custom key for each zram object 2026-08-06 18:57:25 -07:00
fs hugetlb: make hugepage_put_subpool() tolerate NULL 2026-08-06 18:57:20 -07:00
include Merge branch 'mm-hotfixes-stable' into mm-stable to pick up 2026-08-24 18:40:27 -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 cgroup/cpuset: update some comments about the page allocator 2026-08-06 18:57:11 -07:00
lib selftests/mm: add HMM test for mmap lock-dropping faults 2026-08-04 19:18:54 -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: nommu: point to the write iterator upon split_vma 2026-08-24 18:42:48 -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: thuge-gen: fix test_shmget() for PAGE_SIZE check 2026-08-15 21:12:24 -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 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 .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 COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
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 Merge branch 'mm-hotfixes-stable' into mm-stable to pick up 2026-08-24 18:40:27 -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