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Eric Dumazet reported KCSAN warnings: BUG: KCSAN: data-race in pfifo_fast_dequeue / pfifo_fast_enqueue write to 0xffff88811d5ccc00 of 8 bytes by interrupt on cpu 0: __ptr_ring_zero_tail include/linux/ptr_ring.h:259 [inline] __ptr_ring_discard_one include/linux/ptr_ring.h:291 [inline] __ptr_ring_consume include/linux/ptr_ring.h:311 [inline] __skb_array_consume include/linux/skb_array.h:98 [inline] pfifo_fast_dequeue+0x770/0x8f0 net/sched/sch_generic.c:770 dequeue_skb net/sched/sch_generic.c:297 [inline] qdisc_restart net/sched/sch_generic.c:402 [inline] __qdisc_run+0x189/0xc80 net/sched/sch_generic.c:420 qdisc_run include/net/pkt_sched.h:120 [inline] net_tx_action+0x379/0x590 net/core/dev.c:5793 handle_softirqs+0xb9/0x280 kernel/softirq.c:622 do_softirq+0x45/0x60 kernel/softirq.c:523 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450 local_bh_enable include/linux/bottom_half.h:33 [inline] bpf_test_run+0x2db/0x620 net/bpf/test_run.c:426 bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4721 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6246 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline] __se_sys_bpf kernel/bpf/syscall.c:6339 [inline] __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88811d5ccc00 of 8 bytes by task 22632 on cpu 1: __ptr_ring_produce include/linux/ptr_ring.h:106 [inline] ptr_ring_produce include/linux/ptr_ring.h:129 [inline] skb_array_produce include/linux/skb_array.h:44 [inline] pfifo_fast_enqueue+0xd5/0x2c0 net/sched/sch_generic.c:741 dev_qdisc_enqueue net/core/dev.c:4144 [inline] __dev_xmit_skb net/core/dev.c:4188 [inline] __dev_queue_xmit+0x6a4/0x1f20 net/core/dev.c:4795 dev_queue_xmit include/linux/netdevice.h:3384 [inline] __bpf_tx_skb net/core/filter.c:2153 [inline] __bpf_redirect_common net/core/filter.c:2197 [inline] __bpf_redirect+0x862/0x990 net/core/filter.c:2204 ____bpf_clone_redirect net/core/filter.c:2487 [inline] bpf_clone_redirect+0x20c/0x290 net/core/filter.c:2450 bpf_prog_53f18857bc887b09+0x22/0x2a bpf_dispatcher_nop_func include/linux/bpf.h:1402 [inline] __bpf_prog_run include/linux/filter.h:723 [inline] bpf_prog_run include/linux/filter.h:730 [inline] bpf_test_run+0x29d/0x620 net/bpf/test_run.c:423 bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4721 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6246 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline] __se_sys_bpf kernel/bpf/syscall.c:6339 [inline] __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0xffff888104a93a00 -> 0x0000000000000000 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 22632 Comm: syz.0.4135 Tainted: G W syzkaller #0 PREEMPT(full) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 There is no race on ring accesses: reading/writing a partial pointer would be fine, because the reading is done by the producer which merely cares about NULL/non NULL. Document and disable the warnings using data_race(). Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/dd3984b3bce9df3591927f927668cb31cc7ecf34.1774460059.git.mst@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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