Cen Zhang d128ffd2ba xfs: tie zoned sysfs lifetime to zone info
The zoned sysfs directory is currently registered as part of the generic
per-mount sysfs setup, but the data exposed by nr_open_zones has a
narrower lifetime.  mp->m_zone_info is allocated by xfs_mount_zones() and
freed by xfs_unmount_zones(), while the zoned sysfs kobject remained
registered until xfs_mount_sysfs_del().

A read of nr_open_zones can therefore enter through the still-live sysfs
kobject after xfs_unmount_zones() has freed mp->m_zone_info, leading to a
use-after-free in nr_open_zones_show().

Make the zoned sysfs lifetime match the zone-info lifetime inside the zone
allocator.  Create the zoned sysfs directory from xfs_mount_zones() after
the zone allocator has finished setting up, and remove it as the first
step of xfs_unmount_zones(), before any zone allocator teardown can free
m_zone_info.

Sysfs removal deactivates the kernfs nodes and waits for active callbacks
to drain before returning, so this also protects a reader that has already
entered nr_open_zones_show() but has not yet dereferenced m_zone_info.

Validation reproduced this kernel report:
BUG: KASAN: slab-use-after-free in nr_open_zones_show+0x86/0x90
The buggy address belongs to the object at ffff88810b177800 which belongs
to the cache kmalloc-1k of size 1024
The buggy address is located 160 bytes inside of freed 1024-byte region
[ffff88810b177800, ffff88810b177c00)
Read of size 4
Call trace:
  print_report+0xcd/0x620
  nr_open_zones_show+0x86/0x90 (fs/xfs/xfs_sysfs.c:724)
  srso_alias_return_thunk+0x5/0xfbef5
  __virt_addr_valid+0x20c/0x410
  kasan_report+0xdd/0x110
  sysfs_kf_seq_show+0x1bd/0x380
  seq_read_iter+0x40f/0x11b0
  lock_release+0xba/0x260
  mark_held_locks+0x40/0x70
  vfs_read+0x717/0xce0
  __up_read+0x319/0x900
  ksys_read+0xf8/0x1c0
  do_user_addr_fault+0x3d0/0xbc0
  trace_hardirqs_on_prepare+0x23/0xf0
  do_syscall_64+0xc8/0x530 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x74/0x7c
Allocated by task stack:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  __kasan_kmalloc+0xaa/0xb0
  __kmalloc_cache_noprof+0x205/0x460
  xfs_mount_zones+0x34c/0x2650
  xfs_mountfs+0x1b97/0x1eb0
  xfs_fs_fill_super+0xf2b/0x18a0
  get_tree_bdev_flags+0x310/0x590
  vfs_get_tree+0x8d/0x2e0
  __x64_sys_fsconfig+0x61c/0xbc0
  do_syscall_64+0xc8/0x530 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x74/0x7c
Freed by task stack:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  kasan_save_free_info+0x3b/0x60
  __kasan_slab_free+0x5f/0x80
  kfree+0x20e/0x4c0
  xfs_unmountfs+0x2fd/0x390
  xfs_fs_put_super+0x60/0x110
  generic_shutdown_super+0x143/0x4b0
  kill_block_super+0x3b/0x90
  xfs_kill_sb+0x12/0x50
  deactivate_locked_super+0xa7/0x160
  cleanup_mnt+0x218/0x420
  task_work_run+0x11a/0x1f0
  exit_to_user_mode_loop+0x13c/0x4f0
  do_syscall_64+0x4a9/0x530 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x74/0x7c

Fixes: 62c89988dc ("xfs: expose the number of open zones in sysfs")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
2026-07-08 14:54:04 +02:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-06-28 12:01:31 -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
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