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Linus Torvalds 864be1277d tracing fix for 7.2:
- Move rb_desc->nr_page_va before updating dynamic array
 
   The rb_descr->page_va is a dynamic array counted by nr_page_va. But the
   updating of the page_va[] is done before the nr_page_va is incremented
   causing a build with CONFIG_UBSAN_BOUNDS to flag it as an overflow.
 
   Move the increment of the counted by value before the array element is
   updated.
 
 - Propagate errors from remote event bulk updates
 
   The return value of trace_remote_enable_event() was not being checked by
   remote_events_dir_enable_write() where it would silently fail. Have it
   check the return value and propagate that back up to user space.
 
 - Fix resource leak on mmiotrace trace_pipe close
 
   The mmiotrace tracer was created in 2008 before the trace_pipe had a close
   callback to allow tracers to do clean up from trace_pipe open. The
   trace_pipe close cleanup callback was added in 2009 but the mmiotrace
   tracer was not updated. It had a hack to do the cleanup in the read call,
   where it may leak if user space did not read the entire buffer.
 
   Add a callback to mmiotrace trace_pipe close do to the cleanup properly.
 
 - Fix a possible NULL pointer dereference in the mmiotrace tracer
 
   If the mmio_pipe_open() fails to find a PCI device, it will set the
   hiter->dev pointer to NULL. The read function will blindly dereference
   that pointer. Fix the read call to check to see if that pointer is
   populated before dereferencing it.
 
 - Fix union collision of module and refcnt for dynamic events
 
   In 'struct trace_event_call', the 'module' pointer and the 'refcnt' atomic
   variable share the same memory space in a union. The filter on module
   logic only checked if the 'module' was set to determine if the event
   belonged to the module. As dynamic events are always builtin, it doesn't
   need the 'module' field of the structure and used a refcount. But the
   module filtering logic would then mistaken these dynamic events as a
   module and call module_name(event->module) on it.
 
   Add a check to see if the event is a dynamic event and if so, do not check
   it for being part of the given module.
 
 - Reset the top level buffer in selftests before running instances
 
   The ftracetest selftest initializes each instance before executing the
   tests. But it does not reset the top level buffer. Dynamic events are only
   added and removed by the top level so any left over dynamic events will
   not be removed by the reset in the instances.
 
   Left over dynamic events can cause the tests to incorrectly fail. Reset
   the top level buffer before running the instances.
 
 - Make the context_switch counter 64 bit
 
   The code to read user space for a system call trace event or for a
   trace_marker will disable migration, enable preemption, read user space
   into a per CPU buffer, disable preemption and enable migration again.
   It checks if the per CPU context switch counter to see if it changed, and
   if it did not, it would know that the per CPU buffer was not touched by
   another task.
 
   But the save counter was 32 bit and it would compare it to the 64 bit
   context_switch variable. A long running system could have the
   context_switch variable greater that 1<<32 in which case the compare will
   always fail. The compare will promote the 32 bit int saved value to 64 bit
   and compare it to the full 64 bit counter. Since the top 32 bits of the
   saved value was zero, it would never match.
 
 - Fix a use-after-free of the event_enable trigger
 
   The event_enable trigger allows for enabling one event when another event
   is triggered. When the trigger is removed, it must go through a
   synchronization phase to make sure it is not triggered again. The trigger
   itself is delayed by the "bulk delay" logic that was recently added.
   But the code that frees the event_enable data used to rely on the trigger
   code to do the synchronization. Now that the code uses the call RCU
   functions (and a workqueue), that delay no longer is there.
 
   Add a callback private_data_free() function that allows triggers to clean
   up data after the synchronization phase has completed.
 
 - Move the module_ref counter into the delay callback
 
   Since an event of the event_enable trigger can enable an event for a
   module, it ups the module ref count for that event's module. This prevents
   the event from trying to enable an event that no longer exists and cause a
   use-after-free bug.
 
   The ref counter was set back down when the trigger was removed but not
   after thy synchronization phase. This could lead to the module data being
   accessed after module was unloaded.
 
   Move the module ref decrement into the private_data_free() callback of the
   event_enable trigger.
 
 - Add mutex to protect parser in ftrace filtering
 
   The set_ftrace_filter file uses a parsing descriptor that is allocated at
   open and modified by writes. If multiple threads were to write to the
   descriptor at the same time, it can corrupt the parser.
 
   Add a mutex around the modifications of the parser descriptor.
 
 - Fix possible corruption in perf syscall tracing
 
   The perf system call trace events can now read user space. To do so, the
   reads of user space enable preemption and disables it again. During this
   time that preemption is enabled, the task can migrate. The perf event list
   head is assigned via a per CPU pointer. It is done before the user space
   part is called. If the user space reading migrates the task to another
   CPU, then the head pointer is no longer valid.
 
   Re-assign the head pointer after the reading of user space to keep it
   using the correct data.
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Merge tag 'trace-v7.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fixes from Steven Rostedt:

 - Move rb_desc->nr_page_va before updating dynamic array

   The rb_descr->page_va is a dynamic array counted by nr_page_va. But
   the updating of the page_va[] is done before the nr_page_va is
   incremented causing a build with CONFIG_UBSAN_BOUNDS to flag it as an
   overflow.

   Move the increment of the counted by value before the array element
   is updated.

 - Propagate errors from remote event bulk updates

   The return value of trace_remote_enable_event() was not being checked
   by remote_events_dir_enable_write() where it would silently fail.
   Have it check the return value and propagate that back up to user
   space.

 - Fix resource leak on mmiotrace trace_pipe close

   The mmiotrace tracer was created in 2008 before the trace_pipe had a
   close callback to allow tracers to do clean up from trace_pipe open.
   The trace_pipe close cleanup callback was added in 2009 but the
   mmiotrace tracer was not updated. It had a hack to do the cleanup in
   the read call, where it may leak if user space did not read the
   entire buffer.

   Add a callback to mmiotrace trace_pipe close do to the cleanup
   properly.

 - Fix a possible NULL pointer dereference in the mmiotrace tracer

   If the mmio_pipe_open() fails to find a PCI device, it will set the
   hiter->dev pointer to NULL. The read function will blindly
   dereference that pointer. Fix the read call to check to see if that
   pointer is populated before dereferencing it.

 - Fix union collision of module and refcnt for dynamic events

   In 'struct trace_event_call', the 'module' pointer and the 'refcnt'
   atomic variable share the same memory space in a union. The filter on
   module logic only checked if the 'module' was set to determine if the
   event belonged to the module. As dynamic events are always builtin,
   it doesn't need the 'module' field of the structure and used a
   refcount. But the module filtering logic would then mistaken these
   dynamic events as a module and call module_name(event->module) on it.

   Add a check to see if the event is a dynamic event and if so, do not
   check it for being part of the given module.

 - Reset the top level buffer in selftests before running instances

   The ftracetest selftest initializes each instance before executing
   the tests. But it does not reset the top level buffer. Dynamic events
   are only added and removed by the top level so any left over dynamic
   events will not be removed by the reset in the instances.

   Left over dynamic events can cause the tests to incorrectly fail.
   Reset the top level buffer before running the instances.

 - Make the context_switch counter 64 bit

   The code to read user space for a system call trace event or for a
   trace_marker will disable migration, enable preemption, read user
   space into a per CPU buffer, disable preemption and enable migration
   again. It checks if the per CPU context switch counter to see if it
   changed, and if it did not, it would know that the per CPU buffer was
   not touched by another task.

   But the save counter was 32 bit and it would compare it to the 64 bit
   context_switch variable. A long running system could have the
   context_switch variable greater that 1<<32 in which case the compare
   will always fail. The compare will promote the 32 bit int saved value
   to 64 bit and compare it to the full 64 bit counter. Since the top 32
   bits of the saved value was zero, it would never match.

 - Fix a use-after-free of the event_enable trigger

   The event_enable trigger allows for enabling one event when another
   event is triggered. When the trigger is removed, it must go through a
   synchronization phase to make sure it is not triggered again. The
   trigger itself is delayed by the "bulk delay" logic that was recently
   added. But the code that frees the event_enable data used to rely on
   the trigger code to do the synchronization. Now that the code uses
   the call RCU functions (and a workqueue), that delay no longer is
   there.

   Add a callback private_data_free() function that allows triggers to
   clean up data after the synchronization phase has completed.

 - Move the module_ref counter into the delay callback

   Since an event of the event_enable trigger can enable an event for a
   module, it ups the module ref count for that event's module. This
   prevents the event from trying to enable an event that no longer
   exists and cause a use-after-free bug.

   The ref counter was set back down when the trigger was removed but
   not after thy synchronization phase. This could lead to the module
   data being accessed after module was unloaded.

   Move the module ref decrement into the private_data_free() callback
   of the event_enable trigger.

 - Add mutex to protect parser in ftrace filtering

   The set_ftrace_filter file uses a parsing descriptor that is
   allocated at open and modified by writes. If multiple threads were to
   write to the descriptor at the same time, it can corrupt the parser.

   Add a mutex around the modifications of the parser descriptor.

 - Fix possible corruption in perf syscall tracing

   The perf system call trace events can now read user space. To do so,
   the reads of user space enable preemption and disables it again.
   During this time that preemption is enabled, the task can migrate.
   The perf event list head is assigned via a per CPU pointer. It is
   done before the user space part is called. If the user space reading
   migrates the task to another CPU, then the head pointer is no longer
   valid.

   Re-assign the head pointer after the reading of user space to keep it
   using the correct data.

* tag 'trace-v7.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: perf: Fix stale head for perf syscall tracing
  ftrace: Add global mutex to serialize trace_parser access
  tracing: Delay module ref count for "enable_event" trigger
  tracing: Fix use-after-free freeing trigger private data
  tracing: Fix context switch counter truncation
  selftests/ftrace: Reset triggers at top level before instance loop
  tracing: Fix union collision of module and refcnt for dynamic events
  tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev
  tracing: Fix resource leak on mmiotrace trace_pipe close
  tracing: Propagate errors from remote event bulk updates
  tracing/remotes: Fix page_va[] access before counter update in trace_remote_alloc_buffer()
2026-07-26 09:15:59 -07:00
arch m68knommu: fix on top off v7.2-rc4 2026-07-26 08:59:55 -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 Lots of fixes, double the count even for the "new normal". 2026-07-23 12:58:08 -07:00
drivers firewire fixes for 7.2-rc5 2026-07-25 08:14:13 -07:00
fs eight ksmbd server fixes 2026-07-24 19:50:05 -07:00
include io_uring-7.2-20260724 2026-07-24 19:58:03 -07:00
init rust: allow suspicious_runtime_symbol_definitions lint for Rust >= 1.98 2026-06-29 13:02:15 +02:00
io_uring io_uring-7.2-20260724 2026-07-24 19:58:03 -07:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel tracing fix for 7.2: 2026-07-26 09:15:59 -07:00
lib slab fixes for 7.2-rc4 2026-07-24 07:28:35 -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 slab fixes for 7.2-rc4 2026-07-24 07:28:35 -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 tracing fixes for 7.2: 2026-07-12 09:46:37 -07:00
scripts scripts/sorttable: Handle RISC-V patchable ftrace entries 2026-06-25 13:15:03 -06:00
security selinux/stable-7.2 PR 20260717 2026-07-17 11:04:46 -07:00
sound ALSA: hda/realtek - Add quirk for Dell Pro QC1255 2026-07-21 09:55:17 +02:00
tools tracing fix for 7.2: 2026-07-26 09:15:59 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM/arm64 fixes for 7.2, take #2 2026-07-15 12:13:30 +02:00
.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 drm fixes for 7.2-rc5 2026-07-24 14:11:53 -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 CREDITS: Add Wolfram Sang 2026-07-14 16:34:04 +02:00
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 block-7.2-20260724 2026-07-24 20:02:58 -07:00
Makefile Rust fixes for v7.2 (2nd) 2026-07-25 10:15:23 -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