mirror of
https://github.com/torvalds/linux.git
synced 2026-07-28 01:55:51 +02:00
Linux kernel source tree
We ran into below KASAN splat, which is mostly uninteresting, beside
for having nf_nat_register_fn() in the call chain as a cause for the
offending access:
==================================================================
BUG: KASAN: slab-out-of-bounds in nf_nat_register_fn+0x5f9/0x640
Read of size 8 at addr ffff890031e54c20 by task iptables/9510
CPU: 0 UID: 0 PID: 9510 Comm: iptables Not tainted 6.18.18-grsec-full-20260320181326 #1 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
[…] dump_stack_lvl+0xee/0x160 ffff88004117eeb8
[…] print_report+0x6e/0x640 ffff88004117eee0
[…] ? __phys_addr+0x8e/0x140 ffff88004117eef0
[…] ? kasan_addr_to_slab+0x51/0xe0 ffff88004117ef08
[…] ? complete_report_info+0xec/0x1c0 ffff88004117ef20
[…] ? nf_nat_register_fn+0x5f9/0x640 ffff88004117ef48
[…] kasan_report+0xbc/0x140 ffff88004117ef50
[…] ? nf_nat_register_fn+0x5f9/0x640 ffff88004117ef90
[…] nf_nat_register_fn+0x5f9/0x640 ffff88004117eff8
[…] ? nf_nat_icmp_reply_translation+0x6e0/0x6e0 ffff88004117f070
[…] nf_tables_register_hook.part.0+0xa0/0x220 ffff88004117f080
[…] nf_tables_addchain.constprop.0+0x1054/0x1fc0 ffff88004117f0b8
[…] ? nft_chain_lookup.part.0+0x4ce/0xac0 ffff88004117f130
[…] ? nf_tables_abort+0x3d80/0x3d80 ffff88004117f190
[…] ? nf_tables_dumpreset_obj+0x100/0x100 ffff88004117f1c8
[…] ? nft_table_lookup.part.0+0x255/0x300 ffff88004117f310
[…] ? nf_tables_newchain+0x21a4/0x2fa0 ffff88004117f358
[…] nf_tables_newchain+0x21a4/0x2fa0 ffff88004117f360
[…] ? nf_tables_addchain.constprop.0+0x1fc0/0x1fc0 ffff88004117f458
[…] ? nla_get_range_signed+0x4a0/0x4a0 ffff88004117f488
[…] ? lock_acquire+0x16f/0x320 ffff88004117f490
[…] ? find_held_lock+0x3b/0xe0 ffff88004117f4b0
[…] ? __nla_parse+0x45/0x80 ffff88004117f500
[…] nfnetlink_rcv_batch+0xbca/0x19a0 ffff88004117f550
[…] ? nfnetlink_net_exit_batch+0x120/0x120 ffff88004117f618
[…] ? __sanitizer_cov_trace_switch+0x63/0xe0 ffff88004117f720
[…] ? gr_acl_handle_mmap+0x1c4/0x320 ffff88004117f7c0
[…] ? nla_get_range_signed+0x4a0/0x4a0 ffff88004117f7e8
[…] ? gr_is_capable+0x6f/0xe0 ffff88004117f830
[…] ? __nla_parse+0x45/0x80 ffff88004117f860
[…] ? skb_pull+0x103/0x1a0 ffff88004117f880
[…] nfnetlink_rcv+0x3db/0x4a0 ffff88004117f8b0
[…] ? nfnetlink_rcv_batch+0x19a0/0x19a0 ffff88004117f8d8
[…] ? netlink_lookup+0xe2/0x240 ffff88004117f900
[…] netlink_unicast+0x74b/0xb00 ffff88004117f930
[…] ? netlink_attachskb+0xb20/0xb20 ffff88004117f980
[…] ? __check_object_size+0x3e/0xaa0 ffff88004117f998
[…] ? security_netlink_send+0x51/0x160 ffff88004117f9c8
[…] netlink_sendmsg+0xa03/0x1200 ffff88004117f9f8
[…] ? netlink_unicast+0xb00/0xb00 ffff88004117fa70
[…] ? netlink_unicast+0xb00/0xb00 ffff88004117fac8
[…] ? ____sys_sendmsg+0xe2a/0x1040 ffff88004117faf8
[…] ____sys_sendmsg+0xe2a/0x1040 ffff88004117fb00
[…] ? kernel_recvmsg+0x300/0x300 ffff88004117fb60
[…] ? reacquire_held_locks+0xe9/0x260 ffff88004117fbc8
[…] ___sys_sendmsg+0x138/0x200 ffff88004117fbf8
[…] ? do_recvmmsg+0x7e0/0x7e0 ffff88004117fc30
[…] ? lockdep_hardirqs_on_prepare+0x101/0x1e0 ffff88004117fc50
[…] ? lock_acquire+0x16f/0x320 ffff88004117fd20
[…] ? lock_acquire+0x16f/0x320 ffff88004117fd58
[…] ? find_held_lock+0x3b/0xe0 ffff88004117fd70
[…] __sys_sendmsg+0x17a/0x260 ffff88004117fdc8
[…] ? __sys_sendmsg_sock+0x80/0x80 ffff88004117fdf0
[…] ? syscall_trace_enter+0x15e/0x2c0 ffff88004117fe98
[…] do_syscall_64+0x7d/0x400 ffff88004117fec8
[…] entry_SYSCALL_64_safe_stack+0x4a/0x60 ffff88004117fef8
</TASK>
==================================================================
The out-of-bounds report, though, is a red herring as it is for an
access that shouldn't have happened in the first place.
When nf_nat_init() fails to register its BPF kfuncs, it'll unwind and,
among others, call unregister_pernet_subsys() to deregister its per-net
ops. This makes the previously allocated net id available for reuse by
the next caller of register_pernet_subsys(), in our case, synproxy.
However, 'nat_net_id' will still hold the previously allocated value.
If nf_nat.o gets build as a module, all this doesn't matter. A failed
initialization routine makes the module fail to load and any dependent
module won't be able to load either. However, if nf_nat.o is built-in,
a failing init won't /completely/ make its functionality unavailable to
dependent modules, namely the code and static data is still there, free
to be called by modules like nft_chain_nat.ko.
Case in point, nft_chain_nat registers hooks that'll call into nf_nat
which, in our case, failed to initialize and therefore won't have a
valid net id nor related net_nat object any more.
Code in nf_nat, namely nf_nat_register_fn() and nf_nat_unregister_fn(),
still making use of the reallocated net id, lead to a type confusion as
the call to net_generic() will no longer return memory belonging to an
object suited to fit 'struct nat_net' but 'struct synproxy_net' instead.
The latter is only 24 bytes on 64-bit systems, much smaller than struct
nat_net which is 176 bytes, perfectly explaining the OOB KASAN report.
Detect and handle a failed nf_nat_init() by testing the 'nf_nat_hook'
pointer which will be reset to NULL on initialization errors to prevent
the usage of an invalid nat_net pointer.
As this check is only needed when nf_nat.o is built-in, guard it by
'#ifndef MODULE...'.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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