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Ido Schimmel 8b0e69763e mlxsw: spectrum_router: Fix neighbour use-after-free
We sometimes observe use-after-free when dereferencing a neighbour [1].
The problem seems to be that the driver stores a pointer to the
neighbour, but without holding a reference on it. A reference is only
taken when the neighbour is used by a nexthop.

Fix by simplifying the reference counting scheme. Always take a
reference when storing a neighbour pointer in a neighbour entry. Avoid
taking a referencing when the neighbour is used by a nexthop as the
neighbour entry associated with the nexthop already holds a reference.

Tested by running the test that uncovered the problem over 300 times.
Without this patch the problem was reproduced after a handful of
iterations.

[1]
BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x2d4/0x310
Read of size 8 at addr ffff88817f8e3420 by task ip/3929

CPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full)
Hardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023
Call Trace:
 <TASK>
 dump_stack_lvl+0x6f/0xa0
 print_address_description.constprop.0+0x6e/0x300
 print_report+0xfc/0x1fb
 kasan_report+0xe4/0x110
 mlxsw_sp_neigh_entry_update+0x2d4/0x310
 mlxsw_sp_router_rif_gone_sync+0x35f/0x510
 mlxsw_sp_rif_destroy+0x1ea/0x730
 mlxsw_sp_inetaddr_port_vlan_event+0xa1/0x1b0
 __mlxsw_sp_inetaddr_lag_event+0xcc/0x130
 __mlxsw_sp_inetaddr_event+0xf5/0x3c0
 mlxsw_sp_router_netdevice_event+0x1015/0x1580
 notifier_call_chain+0xcc/0x150
 call_netdevice_notifiers_info+0x7e/0x100
 __netdev_upper_dev_unlink+0x10b/0x210
 netdev_upper_dev_unlink+0x79/0xa0
 vrf_del_slave+0x18/0x50
 do_set_master+0x146/0x7d0
 do_setlink.isra.0+0x9a0/0x2880
 rtnl_newlink+0x637/0xb20
 rtnetlink_rcv_msg+0x6fe/0xb90
 netlink_rcv_skb+0x123/0x380
 netlink_unicast+0x4a3/0x770
 netlink_sendmsg+0x75b/0xc90
 __sock_sendmsg+0xbe/0x160
 ____sys_sendmsg+0x5b2/0x7d0
 ___sys_sendmsg+0xfd/0x180
 __sys_sendmsg+0x124/0x1c0
 do_syscall_64+0xbb/0xfd0
 entry_SYSCALL_64_after_hwframe+0x4b/0x53
[...]

Allocated by task 109:
 kasan_save_stack+0x30/0x50
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0x7b/0x90
 __kmalloc_noprof+0x2c1/0x790
 neigh_alloc+0x6af/0x8f0
 ___neigh_create+0x63/0xe90
 mlxsw_sp_nexthop_neigh_init+0x430/0x7e0
 mlxsw_sp_nexthop_type_init+0x212/0x960
 mlxsw_sp_nexthop6_group_info_init.constprop.0+0x81f/0x1280
 mlxsw_sp_nexthop6_group_get+0x392/0x6a0
 mlxsw_sp_fib6_entry_create+0x46a/0xfd0
 mlxsw_sp_router_fib6_replace+0x1ed/0x5f0
 mlxsw_sp_router_fib6_event_work+0x10a/0x2a0
 process_one_work+0xd57/0x1390
 worker_thread+0x4d6/0xd40
 kthread+0x355/0x5b0
 ret_from_fork+0x1d4/0x270
 ret_from_fork_asm+0x11/0x20

Freed by task 154:
 kasan_save_stack+0x30/0x50
 kasan_save_track+0x14/0x30
 __kasan_save_free_info+0x3b/0x60
 __kasan_slab_free+0x43/0x70
 kmem_cache_free_bulk.part.0+0x1eb/0x5e0
 kvfree_rcu_bulk+0x1f2/0x260
 kfree_rcu_work+0x130/0x1b0
 process_one_work+0xd57/0x1390
 worker_thread+0x4d6/0xd40
 kthread+0x355/0x5b0
 ret_from_fork+0x1d4/0x270
 ret_from_fork_asm+0x11/0x20

Last potentially related work creation:
 kasan_save_stack+0x30/0x50
 kasan_record_aux_stack+0x8c/0xa0
 kvfree_call_rcu+0x93/0x5b0
 mlxsw_sp_router_neigh_event_work+0x67d/0x860
 process_one_work+0xd57/0x1390
 worker_thread+0x4d6/0xd40
 kthread+0x355/0x5b0
 ret_from_fork+0x1d4/0x270
 ret_from_fork_asm+0x11/0x20

Fixes: 6cf3c971dc ("mlxsw: spectrum_router: Add private neigh table")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/92d75e21d95d163a41b5cea67a15cd33f547cba6.1764695650.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-12-04 17:53:49 -08:00
arch Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
block vfs-6.19-rc1.inode 2025-12-01 09:02:34 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
Documentation Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
drivers mlxsw: spectrum_router: Fix neighbour use-after-free 2025-12-04 17:53:49 -08:00
fs Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
include Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
init Kbuild updates for v6.19 2025-12-03 14:42:21 -08:00
io_uring vfs-6.19-rc1.fd_prepare.fs 2025-12-01 17:32:07 -08:00
ipc vfs-6.19-rc1.fd_prepare.fs 2025-12-01 17:32:07 -08:00
kernel Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
lib bpf-next-6.19 2025-12-03 16:54:54 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab updates for 6.19 2025-12-03 11:53:47 -08:00
net net/sched: ets: Always remove class from active list before deleting in ets_qdisc_change 2025-12-04 11:43:45 +01:00
rust Rust changes for v6.19 2025-12-03 14:16:49 -08:00
samples Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
scripts Kbuild updates for v6.19 2025-12-03 14:42:21 -08:00
security This update includes the following changes: 2025-12-03 11:28:38 -08:00
sound ALSA: hda/realtek: Add quirk for HP ProBook 450 G8 2025-11-26 07:26:56 +01:00
tools Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt A large overhaul of the restartable sequences and CID management: 2025-12-02 08:48:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap Kbuild updates for v6.19 2025-12-03 14:42:21 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
Makefile Kbuild updates for v6.19 2025-12-03 14:42:21 -08:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -07:00

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


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



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