Eric Dumazet 7fcc2fe39f net: icmp: avoid invalid transport header access in icmp_send tracepoint
syzbot reported a WARNING triggered by DEBUG_NET_WARN_ON_ONCE():

 WARNING: at skb_transport_header include/linux/skbuff.h:3087 [inline]
 WARNING: at udp_hdr include/linux/udp.h:23 [inline]
 WARNING: at do_trace_event_raw_event_icmp_send include/trace/events/icmp.h:30 [inline]
 WARNING: at trace_event_raw_event_icmp_send+0x48c/0x6ec include/trace/events/icmp.h:11
 Call trace:
  skb_transport_header include/linux/skbuff.h:3087 [inline]
  udp_hdr include/linux/udp.h:23 [inline]
  do_trace_event_raw_event_icmp_send include/trace/events/icmp.h:30 [inline]
  trace_event_raw_event_icmp_send+0x48c/0x6ec include/trace/events/icmp.h:11
  __traceiter_icmp_send include/trace/events/icmp.h:11 [inline]
  __do_trace_icmp_send include/trace/events/icmp.h:11 [inline]
  trace_icmp_send+0x320/0x49c include/trace/events/icmp.h:11
  __icmp_send+0xcfc/0x11d8 net/ipv4/icmp.c:1013
  ipv4_send_dest_unreach net/ipv4/route.c:1280 [inline]
  ipv4_link_failure+0x57c/0x8dc net/ipv4/route.c:1287
  dst_link_failure include/net/dst.h:438 [inline]
  vti_tunnel_xmit+0xe40/0x17a4 net/ipv4/ip_vti.c:307

TP_fast_assign() unconditionally calls udp_hdr(skb) before checking
whether the packet is UDP. Furthermore, __icmp_send() can be invoked
from paths (e.g., link failures, ARP errors, forwarding, AF_PACKET)
where skb->transport_header was never initialized (~0U).

Under CONFIG_DEBUG_NET=y, calling skb_transport_header(skb) triggers
DEBUG_NET_WARN_ON_ONCE(!skb_transport_header_was_set(skb)).

Fix this by:
1. Only parsing transport info when iph->protocol == IPPROTO_UDP.
2. Using skb_header_pointer() at skb_network_offset(skb) + (iph->ihl << 2)
   to safely fetch the UDP header without assuming transport_header is set.

Fixes: db3efdcf70 ("net/ipv4: add tracepoint for icmp_send")
Reported-by: syzbot+6d2762674103618994b0@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a8d5538.91706f20.ef82.0009.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Peilin He <he.peilin@zte.com.cn>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20260825084551.1562967-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-08-28 14:58:16 -07:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-07-15 10:51:29 -06:00

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
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