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Linus Torvalds 6205562c59 tracing fixes for 7.2:
- Free field in error path of synthetic event parse
 
   In __create_synth_event() the field was allocated but was not freed in the
   error path.
 
 - Fix ring_buffer_event_length() on 8 byte aligned architectures
 
   On architectures with CONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y,
   the ring_buffer_event_length() may return the wrong size. This
   is because archs with that config set will always use the "big
   event meta header" as that is 8 bytes keeping the payload 8 bytes
   aligned, even when a 4 byte header could hold the size of the
   event.
 
   But ring_buffer_event_length() doesn't take this into account and only
   subtracts 4 bytes for the meta header in the length when it should have
   subtracted 8 bytes.
 
 - Have osnoise wait for a full rcu synchronization on unregister
 
   osnoise_unregister_instance() used to call synchronize_rcu() before
   freeing its copy of the instance but was switched to kfree_rcu().
   The osniose tracer has code that traverses the instances that it
   uses, and inst is just a pointer to that instance. By using kfree_rcu()
   instead of synchronize_rcu(), the instance that the inst pointer is
   pointing to can be freed while the osnoise code is still referencing it.
 
   That is, a rmdir on an instance first unregisters the tracer. When the
   unregister finishes, the rmdir expects that the tracer is finished with
   the instance that it is using. By putting back the synchronize_rcu()
   in osnoise_unregister_instance() the unregistering of osnoise will now
   return when all the users of the instance have finished.
 
 - Remove an unused setting of "ret" in tracing_set_tracer()
 
 - Fix ring_buffer_read_page() copying events
 
   The commit that changed ring_buffer_read_page() to show dropped events
   from the buffer itself, split the "commit" variable between the commit
   value (with flags) and "size" that holds the size of the sub-buffer.
   A cut and paste error changed the test of the reading from checking the
   size of the buffer to the size of the event causing reads to only read one
   event at a time.
 
 - Make tracepoint_printk a static variable
 
   When the tracing sysctl knobs were move from sysctl.c to trace.c, the
   variable tracepoint_printk no longer needed to be global. Make it static.
 
 - Fix some typos
 
 - Fix NULL pointer dereference in func_set_flag()
 
   The flags update of the function tracer first checks if the value of the
   flag is the same and exits if they are, and then it checks if the current
   tracer is the function tracer and exits if it isn't. The problem is that
   these checks need to be in a reversed order, as if the tracer isn't the
   function tracer, then the flag being checked may not exist. Reverse the
   order of these checks.
 
 - Fix ufs core trace events to not dereference a pointer in TP_printk()
 
   The TP_printk() part of the TRACE_EVENT() macro is called when the user
   reads the "trace" file. This can be seconds, minutes, hours, days, weeks,
   and even months after the data was recorded into the ring buffer. Thus,
   saving a pointer to an object into the ring buffer and then dereferencing
   it from TP_printk() can cause harm as the object the pointer is pointing
   to may no longer exist.
 
   Fix all the trace events in ufs core to save the device name in the ring
   buffer instead of dereferencing the device descriptor from TP_printk().
 
 - Prevent out-of-bound reads in glob matching of trace events
 
   The filter logic of events allows simple glob logic to add wild cards to
   filter on strings. But some events have fields that may not have a
   terminating 'nul' character. This may cause the glob matching to go beyond
   the string. Change the logic to always pass in the length of the field
   that is being matched.
 
 - Add no-rcu-check version of trace_##event##_enabled()
 
   The trace_##event##_enabled() usually wraps trace events to do extra work
   that is only needed when the trace event is enabled. But this can hide
   events that are placed in locations where RCU is not watching, and can
   make lockdep not see these bugs when the event is not enabled.
 
   The trace_##event##_enabled() was updated to always test to make sure RCU
   is watching to catch locations that may call events without RCU being
   active.
 
   This caused a false positive for the irq_disabled() and related events. As
   that use trace_irq_disabled_enabled() to force RCU to be watching when the
   event is enabled via the ct_irq_enter() function, calls the event, and
   then calls ct_irq_exit() to put RCU back to its original state.
 
   The trace_irq_disabled_enabled() should not trigger a warning when RCU is
   not watching because the code within its block handles the case properly.
   Make a __trace_##event##_enabled() version for this event to use that
   doesn't check RCU is watching as it handles the case when it isn't.
 
 - Fix use-after-free in user_event_mm_dup()
 
   When the enabler is removed from the link list, it is freed immediately.
   But it is protected via RCU and needs to be freed after an RCU
   grace period. Use queue_rcu_work() so that the event_mutex can also
   be taken as user_event_put() takes the mutex on the last reference
   is released.
 
 - Free type string in error path of parse_synth_field()
 
   There's an error path in parse_synth_field() where the allocated type
   string is not freed.
 
 - Add selftest that tests deferred event teardown
 
 - Fix leak in error path of trace_remote_alloc_buffer()
 
   If page allocation fails, the desc->nr_cpus is not incremented for the
   current CPU and the allocations done for it are not freed.
 
 - Fix allocation length in trace_remote_alloc_buffer()
 
   The logic to calculate the struct_len was doing a double count and setting
   the value too large. Calculate the size upfront to fix the error and
   simplify the logic.
 
 - Fix sparse CPU masks in ring_buffer_desc()
 
   If there are sparse CPUs (gaps in the numbering), the ring_buffer_desc()
   will fail as it tests the CPU number against the number of CPUs that are
   used.
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Merge tag 'trace-v7.2-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fixes from Steven Rostedt:

 - Free field in error path of synthetic event parse

   In __create_synth_event() the field was allocated but was not freed
   in the error path

 - Fix ring_buffer_event_length() on 8 byte aligned architectures

   On architectures with CONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, the
   ring_buffer_event_length() may return the wrong size. This is because
   archs with that config set will always use the "big event meta
   header" as that is 8 bytes keeping the payload 8 bytes aligned, even
   when a 4 byte header could hold the size of the event

   But ring_buffer_event_length() doesn't take this into account and
   only subtracts 4 bytes for the meta header in the length when it
   should have subtracted 8 bytes

 - Have osnoise wait for a full rcu synchronization on unregister

   osnoise_unregister_instance() used to call synchronize_rcu() before
   freeing its copy of the instance but was switched to kfree_rcu(). The
   osniose tracer has code that traverses the instances that it uses,
   and inst is just a pointer to that instance. By using kfree_rcu()
   instead of synchronize_rcu(), the instance that the inst pointer is
   pointing to can be freed while the osnoise code is still referencing
   it

   That is, a rmdir on an instance first unregisters the tracer. When
   the unregister finishes, the rmdir expects that the tracer is
   finished with the instance that it is using. By putting back the
   synchronize_rcu() in osnoise_unregister_instance() the unregistering
   of osnoise will now return when all the users of the instance have
   finished

 - Remove an unused setting of "ret" in tracing_set_tracer()

 - Fix ring_buffer_read_page() copying events

   The commit that changed ring_buffer_read_page() to show dropped
   events from the buffer itself, split the "commit" variable between
   the commit value (with flags) and "size" that holds the size of the
   sub-buffer. A cut and paste error changed the test of the reading
   from checking the size of the buffer to the size of the event causing
   reads to only read one event at a time

 - Make tracepoint_printk a static variable

   When the tracing sysctl knobs were move from sysctl.c to trace.c, the
   variable tracepoint_printk no longer needed to be global. Make it
   static

 - Fix some typos

 - Fix NULL pointer dereference in func_set_flag()

   The flags update of the function tracer first checks if the value of
   the flag is the same and exits if they are, and then it checks if the
   current tracer is the function tracer and exits if it isn't. The
   problem is that these checks need to be in a reversed order, as if
   the tracer isn't the function tracer, then the flag being checked may
   not exist. Reverse the order of these checks

 - Fix ufs core trace events to not dereference a pointer in TP_printk()

   The TP_printk() part of the TRACE_EVENT() macro is called when the
   user reads the "trace" file. This can be seconds, minutes, hours,
   days, weeks, and even months after the data was recorded into the
   ring buffer. Thus, saving a pointer to an object into the ring buffer
   and then dereferencing it from TP_printk() can cause harm as the
   object the pointer is pointing to may no longer exist

   Fix all the trace events in ufs core to save the device name in the
   ring buffer instead of dereferencing the device descriptor from
   TP_printk()

 - Prevent out-of-bound reads in glob matching of trace events

   The filter logic of events allows simple glob logic to add wild cards
   to filter on strings. But some events have fields that may not have a
   terminating 'nul' character. This may cause the glob matching to go
   beyond the string. Change the logic to always pass in the length of
   the field that is being matched

 - Add no-rcu-check version of trace_##event##_enabled()

   The trace_##event##_enabled() usually wraps trace events to do extra
   work that is only needed when the trace event is enabled. But this
   can hide events that are placed in locations where RCU is not
   watching, and can make lockdep not see these bugs when the event is
   not enabled

   The trace_##event##_enabled() was updated to always test to make sure
   RCU is watching to catch locations that may call events without RCU
   being active

   This caused a false positive for the irq_disabled() and related
   events. As that use trace_irq_disabled_enabled() to force RCU to be
   watching when the event is enabled via the ct_irq_enter() function,
   calls the event, and then calls ct_irq_exit() to put RCU back to its
   original state

   The trace_irq_disabled_enabled() should not trigger a warning when
   RCU is not watching because the code within its block handles the
   case properly. Make a __trace_##event##_enabled() version for this
   event to use that doesn't check RCU is watching as it handles the
   case when it isn't

 - Fix use-after-free in user_event_mm_dup()

   When the enabler is removed from the link list, it is freed
   immediately. But it is protected via RCU and needs to be freed after
   an RCU grace period. Use queue_rcu_work() so that the event_mutex can
   also be taken as user_event_put() takes the mutex on the last
   reference is released

 - Free type string in error path of parse_synth_field()

   There's an error path in parse_synth_field() where the allocated type
   string is not freed

 - Add selftest that tests deferred event teardown

 - Fix leak in error path of trace_remote_alloc_buffer()

   If page allocation fails, the desc->nr_cpus is not incremented for
   the current CPU and the allocations done for it are not freed

 - Fix allocation length in trace_remote_alloc_buffer()

   The logic to calculate the struct_len was doing a double count and
   setting the value too large. Calculate the size upfront to fix the
   error and simplify the logic

 - Fix sparse CPU masks in ring_buffer_desc()

   If there are sparse CPUs (gaps in the numbering), the
   ring_buffer_desc() will fail as it tests the CPU number against the
   number of CPUs that are used

* tag 'trace-v7.2-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Allow sparse CPU masks in ring_buffer_desc()
  tracing/remotes: Fix struct_len in trace_remote_alloc_buffer()
  tracing/remotes: Fix leak in trace_remote_alloc_buffer() error path
  selftests/user_events: Wait for deferred event teardown after unregister
  tracing/synthetic: Free type string on error path
  tracing/user_events: Fix use-after-free in user_event_mm_dup()
  tracing: Add a no-rcu-check version of trace_##event##_enabled()
  tracing: Prevent out-of-bounds read in glob matching
  ufs: core: tracing: Do not dereference pointers in TP_printk()
  tracing: Fix NULL pointer dereference in func_set_flag()
  samples: ftrace: Fix typos in benchmark comment
  tracing: Make tracepoint_printk static as not exported
  ring-buffer: Fix ring_buffer_read_page() copying only one event per page
  tracing: Remove unused ret assignment in tracing_set_tracer()
  tracing/osnoise: Call synchronize_rcu() when unregistering
  ring-buffer: Fix event length with forced 8-byte alignment
  tracing/synthetic: Free pending field on error path
2026-07-12 09:46:37 -07:00
arch Misc perf events fixes: 2026-07-11 10:11:45 -07:00
block block: remove redundant GD_NEED_PART_SCAN in add_disk_final() 2026-07-10 09:08:50 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -07:00
Documentation arm64 fixes for -rc3 2026-07-10 09:59:55 -07:00
drivers tracing fixes for 7.2: 2026-07-12 09:46:37 -07:00
fs Misc x86 fixes: 2026-07-11 10:09:23 -07:00
include tracing fixes for 7.2: 2026-07-12 09:46:37 -07:00
init mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -07:00
io_uring io_uring-7.2-20260710 2026-07-11 09:24:38 -07:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel tracing fixes for 7.2: 2026-07-12 09:46:37 -07:00
lib tracing: Prevent out-of-bounds read in glob matching 2026-07-07 10:42:28 -04:00
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: do file ownership checks with the proper mount idmap 2026-07-01 19:02:56 -07:00
net NFS Client Bugfixes for Linux 7.2-rc3 2026-07-10 18:15:26 -07:00
rust Rust changes for v7.2 (addendum) 2026-06-24 15:11:08 -07:00
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 20260710 2026-07-10 18:59:29 -07:00
sound sound fixes for 7.2-rc2 2026-07-05 05:26:45 -10:00
tools tracing fixes for 7.2: 2026-07-12 09:46:37 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt s390: 2026-06-25 10:21:13 -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 20 hotfixes. 17 are for MM. 12 are cc:stable and the remaining 8 2026-07-06 18:51:36 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -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 20 hotfixes. 17 are for MM. 12 are cc:stable and the remaining 8 2026-07-06 18:51:36 -07:00
Makefile Linux 7.2-rc2 2026-07-05 14:44:06 -10:00
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