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Zhang Cen c367b90821 netpoll: normalize skb->dev to the netpoll device
__netpoll_send_skb() always transmits through np->dev and queues busy
packets on np->dev->npinfo->txq, but it leaves skb->dev unchanged.
Stacked callers such as DSA and macvlan can reach netpoll with skb->dev
still naming the upper device while np->dev is the lower device that
owns the netpoll state.

If the skb has to be deferred, queue_process() later dequeues it from
the lower device's txq but retries it through skb->dev. That can
re-enter the upper ndo_start_xmit path on an already transformed skb,
and if the upper device disappears before the lower txq drains the
workqueue can dereference a stale skb->dev pointer.

The buggy scenario involves two paths, with each column showing the
order within that path:

path A label: netpoll enqueue path   path B label: upper-device teardown
1. Stacked xmit calls netpoll        1. Teardown unregisters the upper
   with lower np->dev and upper         net_device while lower npinfo
   skb->dev.                            stays alive.
2. __netpoll_send_skb() uses         2. netdev_release() runs for the
   np->dev->npinfo as the txq           upper net_device.
   owner.
3. Busy transmit queues the skb      3. The lower txq still owns the
   on that lower txq with upper         deferred skb.
   skb->dev.
4. queue_process() drains the        4. queue_process() dereferences
   lower txq and reads skb->dev.        that stale upper skb->dev.

Normalize skb->dev to np->dev after loading np->dev from the netpoll
instance, before either the direct transmit path or the fallback enqueue.
This keeps the queued skb in the same device and txq domain as the
netpoll state that owns it.

KASAN report as below:

KASAN slab-use-after-free in queue_process+0x7c/0x480
Workqueue: events queue_process
The buggy address belongs to the object at ffff88810906c000 which belongs
to the cache kmalloc-4k of size 4096
The buggy address is located 168 bytes inside of freed 4096-byte region
[ffff88810906c000, ffff88810906d000)
Read of size 8
Call trace:
  dump_stack_lvl+0x73/0xb0 (?:?)
  print_report+0xd1/0x620 (?:?)
  srso_alias_return_thunk+0x5/0xfbef5 (?:?)
  __virt_addr_valid+0x215/0x420 (?:?)
  kasan_complete_mode_report_info+0x64/0x200 (?:?)
  kasan_report+0xf7/0x130 (?:?)
  queue_process+0x7c/0x480 (net/core/netpoll.c:88)
  kasan_check_range+0x10c/0x1c0 (?:?)
  __kasan_check_read+0x15/0x20 (?:?)
  process_one_work+0x8b7/0x1af0 (kernel/workqueue.c:3200)
  assign_work+0x170/0x3f0 (?:?)
  worker_thread+0x574/0xf10 (?:?)
  _raw_spin_unlock_irqrestore+0x4b/0x60 (?:?)
  trace_hardirqs_on+0x2a/0x180 (?:?)
  kthread+0x2fc/0x3f0 (?:?)
  ret_from_fork+0x58b/0x830 (?:?)
  __switch_to+0x58e/0xe90 (?:?)
  __switch_to_asm+0x39/0x70 (?:?)
  ret_from_fork_asm+0x1a/0x30 (?:?)
Freed by task stack:
  kasan_save_stack+0x3d/0x60 (?:?)
  kasan_save_track+0x18/0x40 (?:?)
  kasan_save_free_info+0x3f/0x60 (?:?)
  __kasan_slab_free+0x48/0x70 (?:?)
  kfree+0x20e/0x4e0 (?:?)
  kvfree+0x31/0x40 (?:?)
  netdev_release+0x71/0x90 (net/core/net-sysfs.c:2227)
  device_release+0xd2/0x250 (?:?)
  kobject_put+0x181/0x4c0 (lib/kobject.c:730)
  netdev_run_todo+0x700/0x1000 (net/core/dev.c:11666)
  rtnl_dellink+0x396/0xc00 (net/core/rtnetlink.c:3558)
  rtnetlink_rcv_msg+0x740/0xc20 (net/core/rtnetlink.c:6897)
  netlink_rcv_skb+0x147/0x3a0 (?:?)
  rtnetlink_rcv+0x19/0x20 (net/core/rtnetlink.c:7021)
  netlink_unicast+0x4d1/0x830 (net/netlink/af_netlink.c:1327)
  netlink_sendmsg+0x840/0xe10 (net/netlink/af_netlink.c:1812)
  ____sys_sendmsg+0x8a7/0xb50 (?:?)
  ___sys_sendmsg+0x104/0x190 (?:?)
  __sys_sendmsg+0x135/0x1d0 (?:?)
  __x64_sys_sendmsg+0x7b/0xc0 (?:?)
  x64_sys_call+0x205c/0x2130 (?:?)
  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

Fixes: 5de4a473bd ("netpoll queue cleanup")
Signed-off-by: Zhang Cen <rollkingzzc@gmail.com>
Link: https://patch.msgid.link/20260519104647.3517990-1-rollkingzzc@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-05-21 08:10:18 -07:00
Documentation dt-bindings: ethernet: eswin: add optional TXD and RXD delay register offsets 2026-05-21 11:58:16 +02:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
arch Arm: 2026-05-13 11:53:51 -07:00
block block: only read from sqe on initial invocation of blkdev_uring_cmd() 2026-05-05 01:37:12 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto crypto/krb5, rxrpc: Fix lack of pre-decrypt/pre-verify length checks 2026-05-20 16:36:45 -07:00
drivers net: wwan: iosm: fix potential memory leaks in ipc_imem_init() 2026-05-21 08:06:02 -07:00
fs fsverity fix for v7.1-rc3 2026-05-09 11:47:39 -07:00
include tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction 2026-05-20 19:14:06 -07:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260508 2026-05-08 13:12:48 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel audit/stable-7.1 PR 20260513 2026-05-14 08:53:24 -07:00
lib Probes fixes for v7.1-rc3 2026-05-12 10:18:02 -07:00
mm liveupdate fixes for v7.1-rc4 2026-05-13 08:24:50 -07:00
net netpoll: normalize skb->dev to the netpoll device 2026-05-21 08:10:18 -07:00
rust Rust fixes for v7.1 2026-05-09 11:24:02 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts First round of Kbuild fixes for 7.1 2026-04-25 17:04:15 -07:00
security selinux: shrink critical section in sel_write_load() 2026-05-05 16:02:28 -04:00
sound ASoC: Fixes for v7.1 2026-05-06 16:10:00 +02:00
tools selftests: net: Fix checksums in xdp_native 2026-05-21 07:47:00 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-05-12 22:16:16 +02:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.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 Askar 2026-04-15 02:15:02 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap MAINTAINERS: Update address for Michael Grzeschik 2026-05-21 07:47:49 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -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 MAINTAINERS: Update address for Michael Grzeschik 2026-05-21 07:47:49 -07:00
Makefile Linux 7.1-rc3 2026-05-10 14:08:09 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

README

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