drop_monitor: use timer_shutdown_sync() to prevent timer rearming during teardown

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Summary

CVECVE-2026-98286
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 09:18:18 UTC
Updated2026-10-06 09:18:18 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: drop_monitor: use timer_shutdown_sync() to prevent timer rearming during teardown In drop_monitor teardown paths (net_dm_trace_off_set(), net_dm_hw_monitor_stop(), and error unwind paths in net_dm_trace_on_set() and net_dm_hw_monitor_start()), per-CPU timers are stopped using timer_delete_sync() followed by cancel_work_sync(). However, there is a circular dependency between send_timer and dm_alert_work: 1) sched_send_work() (timer callback) schedules dm_alert_work. 2) send_dm_alert() / net_dm_hw_summary_work() calls reset_per_cpu_data() or net_dm_hw_reset_per_cpu_data(). 3) If memory allocation fails under memory pressure in the reset function, it re-arms the timer via mod_timer(&data->send_timer, ...). If dm_alert_work is running concurrently while timer_delete_sync() executes on another CPU, an allocation failure in the worker will re-arm the timer after timer_delete_sync() has already returned. Once cancel_work_sync() completes and module_put() is called, the timer remains active in the timer wheel. If the module is then unloaded, the timer will fire and execute sched_send_work() in freed memory, triggering a kernel panic / use-after-free. Switch from timer_delete_sync() to timer_shutdown_sync(). This guarantees that any in-flight timer handler has finished and prevents subsequent re-arming attempts from running workers from succeeding. When monitoring is restarted later, timer_setup() is invoked, which cleanly re-initializes the timer.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9398e9c0b1d44eeb700e9e766c02bcc765c82570 9616b0c67fbd8cc0b49de7b26cdf2ab33747c80e git Not specified
CNA Linux Linux affected 9398e9c0b1d44eeb700e9e766c02bcc765c82570 bda4d9525fb91a2388ee09669421b8d505290864 git Not specified
CNA Linux Linux affected 9398e9c0b1d44eeb700e9e766c02bcc765c82570 c391a40f71886b28c082b47270f0e856fa3e1150 git Not specified
CNA Linux Linux affected 2514c7ad115e762562c7bdd58bb1ab3425a98245 git Not specified
CNA Linux Linux affected 439b1164da3612ec7e186e1dc314471e7190bfc7 git Not specified
CNA Linux Linux affected 5.10.27 5.11 semver Not specified
CNA Linux Linux affected 5.11.11 5.12 semver Not specified
CNA Linux Linux affected 5.12 Not specified
CNA Linux Linux unaffected 5.12 semver Not specified
CNA Linux Linux unaffected 6.18.54 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.8 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc4 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9616b0c67fbd8cc0b49de7b26cdf2ab33747c80e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bda4d9525fb91a2388ee09669421b8d505290864 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c391a40f71886b28c082b47270f0e856fa3e1150 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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