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Norbert Szetei says: ==================== net: don't strip zerocopy frag markers from a forwarded skb queue_userspace_packet() calls skb_tx_error() on the packet skb in its error path, but it only borrows that skb: on the OVS_ACTION_ATTR_USERSPACE action path do_execute_actions() ignores output_userspace()'s return value and keeps forwarding the same skb through the flow's remaining actions. skb_tx_error() completes the zerocopy uarg and clears SKBFL_ALL_ZEROCOPY, and with it SKBFL_SHARED_FRAG. For a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is what makes esp_input() skb_cow_data() instead of taking the in-place AEAD path. Once it is stripped, a later local ESP delivery decrypts in place over pages the sender still shares with the page cache. Patch 1 moves the skb_tx_error() into the one path that does drop the packet, the "default" arm of ovs_dp_process_packet()'s switch(error). Patch 2 removes a second such strip, in skb_zerocopy(), which calls skb_tx_error() on its source when skb_orphan_frags() fails. A copy helper should not perform a destructive action on its source, and both callers already report the error on their own drop path. MSG_ZEROCOPY skbs cannot reach that one -- SKBFL_DONT_ORPHAN makes skb_orphan_frags() return early -- but producers that do not set that flag, such as vhost-net, can. Patch 3 is new in v2. It stops skb_tx_error() from touching skb_shinfo() state that is shared with clones, so patch 1's new call site cannot reach a live skb either. For a non-last OVS_ACTION_ATTR_RECIRC action clone_execute() sends a skb_clone() into ovs_dp_process_packet() while do_execute_actions() keeps forwarding the original, and skb_clone() does not privatise the frags for these skbs -- skb_orphan_frags() returns early on SKBFL_DONT_ORPHAN -- so a flow miss on the clone strips SKBFL_SHARED_FRAG from the packet still in flight. Confirmed on a KASAN build with a flow matching recirc_id 0 and actions RECIRC(1),OUTPUT(0): with patches 1 and 2 applied it still reproduces the page-cache write, with patch 3 on top it no longer does (5/5 runs). A kprobe on skb_tx_error() shows the datapath drop path is still reached in both cases, so the difference is the guard and not the reproducer. As Ilya noted, that makes patch 3 the general fix -- an skb can enter any skb_tx_error() caller already cloned elsewhere in the stack -- while patches 1 and 2 keep the callers from acting on an skb they do not own. Removing skb_tx_error() altogether looks like the right long-term cleanup and is planned as a net-next follow-up. v3: https://lore.kernel.org/netdev/F3B9E5BA-0AC1-4AD1-A7D9-F38033304270@doyensec.com/ v2: https://lore.kernel.org/netdev/AD1B7BEE-C04C-4A1B-982C-8385F1908911@doyensec.com/ v1: https://lore.kernel.org/netdev/8063260C-05C9-4997-B9B6-2135063C4858@doyensec.com/ ==================== Link: https://patch.msgid.link/4B5CCA6E-2C49-4F86-8C4E-E1BE15C16C0A@doyensec.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
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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