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Duoming Zhou 21d341fe51 net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets 
[ Upstream commit bae8a5d2e7 ]

When the FarSync T-series card is being detached, the fst_card_info is
deallocated in fst_remove_one(). However, the fst_tx_task or fst_int_task
may still be running or pending, leading to use-after-free bugs when the
already freed fst_card_info is accessed in fst_process_tx_work_q() or
fst_process_int_work_q().

A typical race condition is depicted below:

CPU 0 (cleanup)           | CPU 1 (tasklet)
                          | fst_start_xmit()
fst_remove_one()          |   tasklet_schedule()
  unregister_hdlc_device()|
                          | fst_process_tx_work_q() //handler
  kfree(card) //free      |   do_bottom_half_tx()
                          |     card-> //use

The following KASAN trace was captured:

==================================================================
 BUG: KASAN: slab-use-after-free in do_bottom_half_tx+0xb88/0xd00
 Read of size 4 at addr ffff88800aad101c by task ksoftirqd/3/32
 ...
 Call Trace:
  <IRQ>
  dump_stack_lvl+0x55/0x70
  print_report+0xcb/0x5d0
  ? do_bottom_half_tx+0xb88/0xd00
  kasan_report+0xb8/0xf0
  ? do_bottom_half_tx+0xb88/0xd00
  do_bottom_half_tx+0xb88/0xd00
  ? _raw_spin_lock_irqsave+0x85/0xe0
  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  ? __pfx___hrtimer_run_queues+0x10/0x10
  fst_process_tx_work_q+0x67/0x90
  tasklet_action_common+0x1fa/0x720
  ? hrtimer_interrupt+0x31f/0x780
  handle_softirqs+0x176/0x530
  __irq_exit_rcu+0xab/0xe0
  sysvec_apic_timer_interrupt+0x70/0x80
 ...

 Allocated by task 41 on cpu 3 at 72.330843s:
  kasan_save_stack+0x24/0x50
  kasan_save_track+0x17/0x60
  __kasan_kmalloc+0x7f/0x90
  fst_add_one+0x1a5/0x1cd0
  local_pci_probe+0xdd/0x190
  pci_device_probe+0x341/0x480
  really_probe+0x1c6/0x6a0
  __driver_probe_device+0x248/0x310
  driver_probe_device+0x48/0x210
  __device_attach_driver+0x160/0x320
  bus_for_each_drv+0x101/0x190
  __device_attach+0x198/0x3a0
  device_initial_probe+0x78/0xa0
  pci_bus_add_device+0x81/0xc0
  pci_bus_add_devices+0x7e/0x190
  enable_slot+0x9b9/0x1130
  acpiphp_check_bridge.part.0+0x2e1/0x460
  acpiphp_hotplug_notify+0x36c/0x3c0
  acpi_device_hotplug+0x203/0xb10
  acpi_hotplug_work_fn+0x59/0x80
 ...

 Freed by task 41 on cpu 1 at 75.138639s:
  kasan_save_stack+0x24/0x50
  kasan_save_track+0x17/0x60
  kasan_save_free_info+0x3b/0x60
  __kasan_slab_free+0x43/0x70
  kfree+0x135/0x410
  fst_remove_one+0x2ca/0x540
  pci_device_remove+0xa6/0x1d0
  device_release_driver_internal+0x364/0x530
  pci_stop_bus_device+0x105/0x150
  pci_stop_and_remove_bus_device+0xd/0x20
  disable_slot+0x116/0x260
  acpiphp_disable_and_eject_slot+0x4b/0x190
  acpiphp_hotplug_notify+0x230/0x3c0
  acpi_device_hotplug+0x203/0xb10
  acpi_hotplug_work_fn+0x59/0x80
 ...

 The buggy address belongs to the object at ffff88800aad1000
  which belongs to the cache kmalloc-1k of size 1024
 The buggy address is located 28 bytes inside of
  freed 1024-byte region
 The buggy address belongs to the physical page:
 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xaad0
 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
 flags: 0x100000000000040(head|node=0|zone=1)
 page_type: f5(slab)
 raw: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000
 raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
 head: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000
 head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
 head: 0100000000000003 ffffea00002ab401 00000000ffffffff 00000000ffffffff
 head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
 page dumped because: kasan: bad access detected

 Memory state around the buggy address:
  ffff88800aad0f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88800aad0f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 >ffff88800aad1000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff88800aad1080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff88800aad1100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ==================================================================

Fix this by ensuring that both fst_tx_task and fst_int_task are properly
canceled before the fst_card_info is released. Add tasklet_kill() in
fst_remove_one() to synchronize with any pending or running tasklets.
Since unregister_hdlc_device() stops data transmission and reception,
and fst_disable_intr() prevents further interrupts, it is appropriate
to place tasklet_kill() after these calls.

The bugs were identified through static analysis. To reproduce the issue
and validate the fix, a FarSync T-series card was simulated in QEMU and
delays(e.g., mdelay()) were introduced within the tasklet handler to
increase the likelihood of triggering the race condition.

Fixes: 2f623aaf9f ("net: farsync: Fix kmemleak when rmmods farsync")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Jijie Shao <shaojijie@huawei.com>
Link: https://patch.msgid.link/20260219124637.72578-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:20:49 -05:00
arch arm64: hugetlbpage: avoid unused-but-set-parameter warning (gcc-16) 2026-03-04 07:20:42 -05:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:19:38 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation ipv6: Move ipv6_fl_list from ipv6_pinfo to inet_sock. 2026-03-04 07:20:44 -05:00
drivers net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets 2026-03-04 07:20:49 -05:00
fs ksmbd: fix signededness bug in smb_direct_prepare_negotiation() 2026-03-04 07:20:46 -05:00
include Bluetooth: L2CAP: Fix result of L2CAP_ECRED_CONN_RSP when MTU is too short 2026-03-04 07:20:47 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/timeout: annotate data race in io_flush_timeouts() 2026-03-04 07:19:36 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel Remove WARN_ALL_UNSEEDED_RANDOM kernel config option 2026-03-04 07:20:46 -05:00
lib Remove WARN_ALL_UNSEEDED_RANDOM kernel config option 2026-03-04 07:20:46 -05:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: fix false lockdep warning in __kfree_rcu_sheaf() 2026-02-26 14:59:14 -08:00
net tipc: fix duplicate publication key in tipc_service_insert_publ() 2026-03-04 07:20:48 -05:00
rust rust: cpufreq: always inline functions using build_assert with arguments 2026-03-04 07:19:37 -05:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts modpost: Amend ppc64 save/restfpr symnames for -Os build 2026-03-04 07:20:07 -05:00
security apparmor: fix aa_label to return state from compount and component match 2026-02-26 14:59:42 -08:00
sound ALSA: hda/hdmi: Add quirk for TUXEDO IBS14G6 2026-03-04 07:20:42 -05:00
tools rtla: Fix NULL pointer dereference in actions_parse 2026-03-04 07:20:13 -05:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.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 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 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 .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: 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 soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.15 2026-02-27 16:05:10 -05:00
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.