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Pull tracing fixes from Steven Rostedt: - Fix use-after-free in eventfs_remove_rec() The freeing of the eventfs_inode children used list_for_each_entry() where the child is freed via srcu, but there's still a chance that it gets freed. It should be using list_for_each_entry_safe(). - Fix eventfs_inode SRCU use of list in freeing The iterator uses an SRCU protected list walk on the eventfs inodes. The eventfs inode uses its "list" field in a union with the RCU list head. When the inode gets added to the SRCU list it immediately corrupts the list pointer and can cause an issue with the iterator. Move the RCU list head to be shared with the children list head which allows the iterator to check the parent inode if is freed before referencing the child. Have the iterator check the parent "is_freed" field and break out if it is set. Also add memory barriers to make sure the ordering is correct. - Fix various RCU synchronization issues with direct_functions Updates to direct_functions have some missing RCU protection and synchronization. Restructure the code a bit to make sure updates to the direct_functions are protected. - Remove an unneeded comma from a scope_guard() There's a spurious comma in a scope_guard(). Remove it. - Fix race in per CPU buffer swap in the ring buffer When a per CPU buffer swap happens, it must make sure that it doesn't occur while a writer is active. Instead it returns an -EBUSY. But there's a small race window when a writer moves from one sub-buffer to the next that it resets the "committing" counter. If a swap happens at that moment, the buffer used for the commit of an event will not match the buffer the event is actually on. Instead of using the "committing" counter, use the recursive detection counter that does not get reset when the writer crosses sub-buffers. - Fix off-by-one in ftrace_free_mem() The function ftrace_free_mem() gets an "end_ptr" as a parameter that is exclusive to the rang to be freed. But its value is used to search for the records that expects an inclusive value. Subtract one from the parameter to convert it to an inclusive range. - Disable resizing of the ring buffer for persistent buffers Resizing the persistent buffer has undefined behavior. Prevent it from being resized. - Disable changing ring buffer subbuf order when resizing is disabled The ring buffer subbuffer order can not be changed during resizing. Use that instead of just checking if the buffer is mapped as mapped buffers also have resizing disabled. - Initialize subbuf_order of reader pages when they are created In rb_allocate_cpu_buffer() the bpage->order is not updated to the current subbuf_order leaving it as zero. This value is used when the page is freed. - Fix test_ringbuffer() to test for ERR_PTR before calling kthread_stop() The rb_threads[] array is assigned the output of kthread_run_on_cpu() which could return an ERR_PTR. At the end of the test, all threads in the array are cleaned up by kthread_stop() passing in the value in the array if it isn't zero. But if the array contains an ERR_PTR, kthread_stop() will not be able to handle it properly. * tag 'trace-v7.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Fix crash passing ERR_PTR to kthread_stop() ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer() ring-buffer: Prevent subbuf order change when resizing is disabled ring-buffer: Prevent resizing of persistent ring buffer ftrace: Fix off-by-one fentry site disable in ftrace_free_mem() ring-buffer: Use current_context for safe per-CPU buffer swap ftrace: Drop extra comma in trace_buffered_event_enable ftrace: Protect direct_functions in update_ftrace_direct_mod ftrace: Protect direct_functions in update_ftrace_direct_del ftrace: Protect direct_functions in ftrace_find_rec_direct eventfs: Use children field for rcu head and add memory barriers eventfs: Fix use-after-free in eventfs_remove_rec()
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. 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