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Cen Zhang 88496c4ac5 ntfs: avoid stale runlist element dereference in fallocate
ntfs_attr_fallocate() allocates holes and delayed allocations inside
initialized size by looking up the current runlist element under
ni->runlist.lock. The returned struct runlist_element is only a borrowed
pointer into ni->runlist.rl. A writer can replace and free that array
after the read lock is dropped, so later reads of rl->lcn, rl->length and
rl->vcn can touch freed memory.

The buggy scenario involves two paths, with each column showing the order
within that path:

ntfs_attr_fallocate():
  1. Take ni->runlist.lock for read.
  2. Get rl from ntfs_attr_find_vcn_nolock().
  3. Drop ni->runlist.lock.
  4. Read rl->lcn, rl->length and rl->vcn.

mmap page_mkwrite:
  1. Enter ntfs_filemap_page_mkwrite().
  2. Reach __ntfs_write_iomap_begin() and ntfs_attr_map_cluster().
  3. Merge allocation state with ntfs_runlists_merge().
  4. Reallocate ni->runlist.rl in ntfs_rl_realloc(), freeing the old array.

Validation reproduced this kernel report:
BUG: KASAN: slab-use-after-free in ntfs_attr_fallocate+0xbb8/0xd00

Call Trace:
 <TASK>
 dump_stack_lvl+0x66/0xa0
 print_report+0xce/0x630
 ? ntfs_attr_fallocate+0xbb8/0xd00
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __virt_addr_valid+0x20d/0x410
 ? ntfs_attr_fallocate+0xbb8/0xd00
 kasan_report+0xe0/0x110
 ? ntfs_attr_fallocate+0xbb8/0xd00
 ntfs_attr_fallocate+0xbb8/0xd00
 ? lock_acquire+0x2b8/0x2f0
 ? __pfx_ntfs_attr_fallocate+0x10/0x10
 ? 0xffffffffc0000095
 ? down_write+0x10d/0x1e0
 ntfs_fallocate+0x5c9/0x1d00
 ? __pfx_ntfs_fallocate+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lock_acquire+0x2b8/0x2f0
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? selinux_file_permission+0x3a7/0x510
 vfs_fallocate+0x29d/0xd30
 __x64_sys_fallocate+0xc7/0x150
 ? do_syscall_64+0x81/0x6a0
 do_syscall_64+0x115/0x6a0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Allocated by task 410:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0xaa/0xb0
 __kvmalloc_node_noprof+0x353/0x920
 ntfs_rl_realloc+0x3f/0x110
 ntfs_runlists_merge+0xaa3/0x3010
 ntfs_attr_map_cluster+0x4e5/0xf80
 ntfs_attr_fallocate+0x53f/0xd00
 ntfs_fallocate+0x5c9/0x1d00
 vfs_fallocate+0x29d/0xd30
 __x64_sys_fallocate+0xc7/0x150
 do_syscall_64+0x115/0x6a0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 424:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3b/0x60
 __kasan_slab_free+0x5f/0x80
 kfree+0x307/0x580
 ntfs_rl_realloc+0x6f/0x110
 ntfs_runlists_merge+0x7b1/0x3010
 ntfs_attr_map_cluster+0x4e5/0xf80
 __ntfs_write_iomap_begin+0x8cd/0x2280
 iomap_iter+0x6de/0x11e0
 iomap_page_mkwrite+0x391/0x650
 ntfs_filemap_page_mkwrite+0x1ac/0x400
 do_page_mkwrite+0x15c/0x280
 __handle_mm_fault+0xd6d/0x1ca0
 handle_mm_fault+0x19c/0x470
 do_user_addr_fault+0x23b/0x9c0
 exc_page_fault+0x5c/0xc0
 asm_exc_page_fault+0x26/0x30

Fix this by copying the needed runlist fields while the read lock is still
held and using only those scalar snapshots after unlocking.

After the snapshot, ntfs_attr_map_cluster() can also find that the range
is already mapped and return balloc=false. Only call ntfs_dio_zero_range()
when new clusters were allocated, matching the write iomap path and
preserving the zero-newly-allocated-holes behavior.

Fixes: 495e90fa33 ("ntfs: update attrib operations")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
2026-06-30 23:19:36 +09:00
arch strncpy removal for v7.2-rc1 2026-06-19 14:56:45 -07:00
block - small cleanups in dm-vdo, dm-raid, dm-cache, dm-zoned-metadata 2026-06-16 13:20:54 +05:30
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto Networking changes for 7.2. 2026-06-17 08:17:00 +01:00
Documentation strncpy removal for v7.2-rc1 2026-06-19 14:56:45 -07:00
drivers strncpy removal for v7.2-rc1 2026-06-19 14:56:45 -07:00
fs ntfs: avoid stale runlist element dereference in fallocate 2026-06-30 23:19:36 +09:00
include strncpy removal for v7.2-rc1 2026-06-19 14:56:45 -07:00
init Bootconfig updates for v7.2 2026-06-16 17:29:24 +05:30
io_uring for-7.2/io_uring-epoll-20260616 2026-06-18 08:09:57 -07:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
lib strncpy removal for v7.2-rc1 2026-06-19 14:56:45 -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.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
net mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
rust mm.git review status for mm-hotfixes-stable..mm-stable 2026-06-19 10:14:34 -07:00
samples Landlock update for v7.2-rc1 2026-06-19 12:20:25 -07:00
scripts Devicetree updates for v7.2: 2026-06-17 11:54:57 -07:00
security Landlock update for v7.2-rc1 2026-06-19 12:20:25 -07:00
sound sound updates for 7.2-rc1 2026-06-17 11:18:45 +01:00
tools Landlock update for v7.2-rc1 2026-06-19 12:20:25 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt Arm: 2026-06-19 08:56:49 -07:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.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 Rust changes for v7.2 2026-06-15 09:25:48 +05:30
.mailmap Updates for the 7.2 release 2026-06-18 16:27:58 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS MFD for v7.2 2026-06-18 14:26:29 -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 integrity-v7.2 2026-06-19 11:32:05 -07:00
Makefile Devicetree updates for v7.2: 2026-06-17 11:54:57 -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