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Duoming Zhou 70acdd1eb3 net: mscc: ocelot: Fix use-after-free caused by cyclic delayed work 
[ Upstream commit bc9ea78707 ]

The origin code calls cancel_delayed_work() in ocelot_stats_deinit()
to cancel the cyclic delayed work item ocelot->stats_work. However,
cancel_delayed_work() may fail to cancel the work item if it is already
executing. While destroy_workqueue() does wait for all pending work items
in the work queue to complete before destroying the work queue, it cannot
prevent the delayed work item from being rescheduled within the
ocelot_check_stats_work() function. This limitation exists because the
delayed work item is only enqueued into the work queue after its timer
expires. Before the timer expiration, destroy_workqueue() has no visibility
of this pending work item. Once the work queue appears empty,
destroy_workqueue() proceeds with destruction. When the timer eventually
expires, the delayed work item gets queued again, leading to the following
warning:

workqueue: cannot queue ocelot_check_stats_work on wq ocelot-switch-stats
WARNING: CPU: 2 PID: 0 at kernel/workqueue.c:2255 __queue_work+0x875/0xaf0
...
RIP: 0010:__queue_work+0x875/0xaf0
...
RSP: 0018:ffff88806d108b10 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000101 RCX: 0000000000000027
RDX: 0000000000000027 RSI: 0000000000000004 RDI: ffff88806d123e88
RBP: ffffffff813c3170 R08: 0000000000000000 R09: ffffed100da247d2
R10: ffffed100da247d1 R11: ffff88806d123e8b R12: ffff88800c00f000
R13: ffff88800d7285c0 R14: ffff88806d0a5580 R15: ffff88800d7285a0
FS:  0000000000000000(0000) GS:ffff8880e5725000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe18e45ea10 CR3: 0000000005e6c000 CR4: 00000000000006f0
Call Trace:
 <IRQ>
 ? kasan_report+0xc6/0xf0
 ? __pfx_delayed_work_timer_fn+0x10/0x10
 ? __pfx_delayed_work_timer_fn+0x10/0x10
 call_timer_fn+0x25/0x1c0
 __run_timer_base.part.0+0x3be/0x8c0
 ? __pfx_delayed_work_timer_fn+0x10/0x10
 ? rcu_sched_clock_irq+0xb06/0x27d0
 ? __pfx___run_timer_base.part.0+0x10/0x10
 ? try_to_wake_up+0xb15/0x1960
 ? _raw_spin_lock_irq+0x80/0xe0
 ? __pfx__raw_spin_lock_irq+0x10/0x10
 tmigr_handle_remote_up+0x603/0x7e0
 ? __pfx_tmigr_handle_remote_up+0x10/0x10
 ? sched_balance_trigger+0x1c0/0x9f0
 ? sched_tick+0x221/0x5a0
 ? _raw_spin_lock_irq+0x80/0xe0
 ? __pfx__raw_spin_lock_irq+0x10/0x10
 ? tick_nohz_handler+0x339/0x440
 ? __pfx_tmigr_handle_remote_up+0x10/0x10
 __walk_groups.isra.0+0x42/0x150
 tmigr_handle_remote+0x1f4/0x2e0
 ? __pfx_tmigr_handle_remote+0x10/0x10
 ? ktime_get+0x60/0x140
 ? lapic_next_event+0x11/0x20
 ? clockevents_program_event+0x1d4/0x2a0
 ? hrtimer_interrupt+0x322/0x780
 handle_softirqs+0x16a/0x550
 irq_exit_rcu+0xaf/0xe0
 sysvec_apic_timer_interrupt+0x70/0x80
 </IRQ>
...

The following diagram reveals the cause of the above warning:

CPU 0 (remove)             | CPU 1 (delayed work callback)
mscc_ocelot_remove()       |
  ocelot_deinit()          | ocelot_check_stats_work()
    ocelot_stats_deinit()  |
      cancel_delayed_work()|   ...
                           |   queue_delayed_work()
      destroy_workqueue()  | (wait a time)
                           | __queue_work() //UAF

The above scenario actually constitutes a UAF vulnerability.

The ocelot_stats_deinit() is only invoked when initialization
failure or resource destruction, so we must ensure that any
delayed work items cannot be rescheduled.

Replace cancel_delayed_work() with disable_delayed_work_sync()
to guarantee proper cancellation of the delayed work item and
ensure completion of any currently executing work before the
workqueue is deallocated.

A deadlock concern was considered: ocelot_stats_deinit() is called
in a process context and is not holding any locks that the delayed
work item might also need. Therefore, the use of the _sync() variant
is safe here.

This bug was identified through static analysis. To reproduce the
issue and validate the fix, I simulated ocelot-switch device by
writing a kernel module and prepared the necessary resources for
the virtual ocelot-switch device's probe process. Then, removing
the virtual device will trigger the mscc_ocelot_remove() function,
which in turn destroys the workqueue.

Fixes: a556c76adc ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://patch.msgid.link/20251001011149.55073-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-19 16:33:40 +02:00
arch LoongArch: Init acpi_gbl_use_global_lock to false 2025-10-19 16:33:39 +02:00
block block: use int to store blk_stack_limits() return value 2025-10-15 11:59:58 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto KEYS: X.509: Fix Basic Constraints CA flag parsing 2025-10-15 12:00:18 +02:00
Documentation Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram 2025-10-15 12:00:13 +02:00
drivers net: mscc: ocelot: Fix use-after-free caused by cyclic delayed work 2025-10-19 16:33:40 +02:00
fs listmount: don't call path_put() under namespace semaphore 2025-10-19 16:33:34 +02:00
include asm-generic/io.h: Skip trace helpers if rwmmio events are disabled 2025-10-19 16:33:35 +02:00
init init: INITRAMFS_PRESERVE_MTIME should depend on BLK_DEV_INITRD 2025-10-15 11:59:53 +02:00
io_uring io_uring/waitid: always prune wait queue entry in io_waitid_wait() 2025-10-15 12:00:20 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel rseq: Protect event mask against membarrier IPI 2025-10-19 16:33:34 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:30:49 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: hugetlb: avoid soft lockup when mprotect to large memory area 2025-10-15 12:00:23 +02:00
net tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). 2025-10-19 16:33:40 +02:00
rust rust: block: fix srctree/ links 2025-10-12 12:57:16 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security lsm: CONFIG_LSM can depend on CONFIG_SECURITY 2025-10-15 11:59:55 +02:00
sound ASoC: SOF: Intel: Read the LLP via the associated Link DMA channel 2025-10-19 16:33:39 +02:00
tools perf evsel: Ensure the fallback message is always written to 2025-10-19 16:33:37 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.53 2025-10-15 12:00:25 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.