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BPF_REG_PARAMS (R11) is at index MAX_BPF_REG, which is beyond the register tracking arrays in const_fold.c and liveness.c. Handle it explicitly to avoid out-of-bounds accesses. Extend the arg tracking dataflow to cover stack arg slots. Otherwise, pointers passed through stack args are invisible to liveness, causing the pointed-to stack slots to be incorrectly poisoned. Extend the at_out tracking array to MAX_AT_TRACK_REGS (registers plus stack arg slots) so that outgoing stack arg stores are tracked alongside registers. Add a separate at_stack_arg_entry array in compute_subprog_args(), passed to arg_track_xfer(), to restore FP-derived values on incoming stack arg reads. Extend record_call_access() to check stack arg slots for FP-derived pointers at kfunc call sites, reusing the record_arg_access() helper extracted in the previous patch. Pass stack arg state from caller to callee in analyze_subprog() so that callees can track pointers received through stack args, hence avoid poisoning. Skip stack arg instructions in record_load_store_access(). Stack arg STX uses dst_reg=BPF_REG_PARAMS (index 11), but at[11] is repurposed to track the value stored in stack arg slot 0. Without the skip, if a prior stack arg STX stored an FP-derived pointer (e.g., fp-64) into slot 0, a subsequent stack arg STX would read that FP-derived value as the base pointer and spuriously mark a regular stack slot (e.g., fp-72 from -64 + -8) as accessed in the liveness bitmap. Extend arg_track_log() to log state transitions for outgoing stack arg slots at indices MAX_BPF_REG through MAX_AT_TRACK_REGS-1. Without this, changes to at_out[11..17] caused by stack arg store instructions are silently omitted from BPF_LOG_LEVEL2 output. For example, when a caller passes fp-64 through a stack argument: subprog#0: 10: (bf) r6 = r10 11: (07) r6 += -64 12: (7b) *(u64 *)(r11 -8) = r6 sa0: none -> fp0-64 13: (85) call pc+5 Without the fix, the "sa0: none -> fp0-64" transition at insn 12 would not appear. Extend print_subprog_arg_access() to include stack arg slots in the per-instruction FP-derived state dump. For example: subprog#0: 12: (7b) *(u64 *)(r11 - 8) = r6 // r6=fp0-64 13: (85) call pc+5 // r6=fp0-64 sa0=fp0-64 Without the fix, the "sa0=fp0-64" annotation at insn 13 would not appear, making it harder to debug liveness analysis for programs that pass FP-derived pointers through stack arguments. Extend has_fp_args() to also check stack arg slots for FP-derived pointers, so that callees receiving pointers only through stack args are still recursively analyzed. Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20260513045043.2389049-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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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