CVE: CVE-2025-39995
Published: 2025-10-15
Description: In the Linux kernel, the following vulnerability has been resolved:

media: i2c: tc358743: Fix use-after-free bugs caused by orphan timer in probe

The state->timer is a cyclic timer that schedules work_i2c_poll and
delayed_work_enable_hotplug, while rearming itself. Using timer_delete()
fails to guarantee the timer isn't still running when destroyed, similarly
cancel_delayed_work() cannot ensure delayed_work_enable_hotplug has
terminated if already executing. During probe failure after timer
initialization, these may continue running as orphans and reference the
already-freed tc358743_state object through tc358743_irq_poll_timer.

The following is the trace captured by KASAN.

BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x7d7/0x8c0
Write of size 8 at addr ffff88800ded83c8 by task swapper/1/0
...
Call Trace:
 <IRQ>
 dump_stack_lvl+0x55/0x70
 print_report+0xcf/0x610
 ? __pfx_sched_balance_find_src_group+0x10/0x10
 ? __run_timer_base.part.0+0x7d7/0x8c0
 kasan_report+0xb8/0xf0
 ? __run_timer_base.part.0+0x7d7/0x8c0
 __run_timer_base.part.0+0x7d7/0x8c0
 ? rcu_sched_clock_irq+0xb06/0x27d0
 ? __pfx___run_timer_base.part.0+0x10/0x10
 ? try_to_wake_up+0xb15/0x1960
 ? tmigr_update_events+0x280/0x740
 ? _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+0x98/0x9f0
 ? 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>
...

Allocated by task 141:
 kasan_save_stack+0x24/0x50
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0x7f/0x90
 __kmalloc_node_track_caller_noprof+0x198/0x430
 devm_kmalloc+0x7b/0x1e0
 tc358743_probe+0xb7/0x610  i2c_device_probe+0x51d/0x880
 really_probe+0x1ca/0x5c0
 __driver_probe_device+0x248/0x310
 driver_probe_device+0x44/0x120
 __device_attach_driver+0x174/0x220
 bus_for_each_drv+0x100/0x190
 __device_attach+0x206/0x370
 bus_probe_device+0x123/0x170
 device_add+0xd25/0x1470
 i2c_new_client_device+0x7a0/0xcd0
 do_one_initcall+0x89/0x300
 do_init_module+0x29d/0x7f0
 load_module+0x4f48/0x69e0
 init_module_from_file+0xe4/0x150
 idempotent_init_module+0x320/0x670
 __x64_sys_finit_module+0xbd/0x120
 do_syscall_64+0xac/0x280
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 141:
 kasan_save_stack+0x24/0x50
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3a/0x60
 __kasan_slab_free+0x3f/0x50
 kfree+0x137/0x370
 release_nodes+0xa4/0x100
 devres_release_group+0x1b2/0x380
 i2c_device_probe+0x694/0x880
 really_probe+0x1ca/0x5c0
 __driver_probe_device+0x248/0x310
 driver_probe_device+0x44/0x120
 __device_attach_driver+0x174/0x220
 bus_for_each_drv+0x100/0x190
 __device_attach+0x206/0x370
 bus_probe_device+0x123/0x170
 device_add+0xd25/0x1470
 i2c_new_client_device+0x7a0/0xcd0
 do_one_initcall+0x89/0x300
 do_init_module+0x29d/0x7f0
 load_module+0x4f48/0x69e0
 init_module_from_file+0xe4/0x150
 idempotent_init_module+0x320/0x670
 __x64_sys_finit_module+0xbd/0x120
 do_syscall_64+0xac/0x280
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
...

Replace timer_delete() with timer_delete_sync() and cancel_delayed_work()
with cancel_delayed_work_sync() to ensure proper termination of timer and
work items before resource cleanup.

This bug was initially identified through static analysis. For reproduction
and testing, I created a functional emulation of the tc358743 device via a
kernel module and introduced faults through the debugfs interface.
References: https://git.kernel.org/stable/c/228d06c4cbfc750f1216a3fd91b4693b0766d2f6; https://git.kernel.org/stable/c/2610617effb4454d2f1c434c011ccb5cc7140711; https://git.kernel.org/stable/c/3d17701c[PII_REDACTED]0e58b3a906511f8bc018d