CVE-2025-39945
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: cnic: Fix use-after-free bugs in cnic_delete_task The original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(), which does not guarantee that the delayed work item 'delete_task' has fully completed if it was already running. Additionally, the delayed work item is cyclic, the flush_workqueue() in cnic_cm_stop_bnx2x_hw() only blocks and waits for work items that were already queued to the workqueue prior to its invocation. Any work items submitted after flush_workqueue() is called are not included in the set of tasks that the flush operation awaits. This means that after the cyclic work items have finished executing, a delayed work item may still exist in the workqueue. This leads to use-after-free scenarios where the cnic_dev is deallocated by cnic_free_dev(), while delete_task remains active and attempt to dereference cnic_dev in cnic_delete_task(). A typical race condition is illustrated below: CPU 0 (cleanup) | CPU 1 (delayed work callback) cnic_netdev_event() | cnic_stop_hw() | cnic_delete_task() cnic_cm_stop_bnx2x_hw() | ... cancel_delayed_work() | /* the queue_delayed_work() flush_workqueue() | executes after flush_workqueue()*/ | queue_delayed_work() cnic_free_dev(dev)//free | cnic_delete_task() //new instance | dev = cp->dev; //use Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the cyclic delayed work item is properly canceled and that any ongoing execution of the work item completes before the cnic_dev is deallocated. Furthermore, since cancel_delayed_work_sync() uses __flush_work(work, true) to synchronously wait for any currently executing instance of the work item to finish, the flush_workqueue() becomes redundant and should be removed. This bug was identified through static analysis. To reproduce the issue and validate the fix, I simulated the cnic PCI device in QEMU and introduced intentional delays — such as inserting calls to ssleep() within the cnic_delete_task() function — to increase the likelihood of triggering the bug.
Severity
HIGH
CVSS score
7.8
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-04 08:15:47.613000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON
{
"id": "CVE-2025-39945",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-04T08:15:47.613",
"lastModified": "2026-10-19T21:10:00.160",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncnic: Fix use-after-free bugs in cnic_delete_task\n\nThe original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(),\nwhich does not guarantee that the delayed work item 'delete_task' has\nfully completed if it was already running. Additionally, the delayed work\nitem is cyclic, the flush_workqueue() in cnic_cm_stop_bnx2x_hw() only\nblocks and waits for work items that were already queued to the\nworkqueue prior to its invocation. Any work items submitted after\nflush_workqueue() is called are not included in the set of tasks that the\nflush operation awaits. This means that after the cyclic work items have\nfinished executing, a delayed work item may still exist in the workqueue.\nThis leads to use-after-free scenarios where the cnic_dev is deallocated\nby cnic_free_dev(), while delete_task remains active and attempt to\ndereference cnic_dev in cnic_delete_task().\n\nA typical race condition is illustrated below:\n\nCPU 0 (cleanup) | CPU 1 (delayed work callback)\ncnic_netdev_event() |\n cnic_stop_hw() | cnic_delete_task()\n cnic_cm_stop_bnx2x_hw() | ...\n cancel_delayed_work() | /* the queue_delayed_work()\n flush_workqueue() | executes after flush_workqueue()*/\n | queue_delayed_work()\n cnic_free_dev(dev)//free | cnic_delete_task() //new instance\n | dev = cp->dev; //use\n\nReplace cancel_delayed_work() with cancel_delayed_work_sync() to ensure\nthat the cyclic delayed work item is properly canceled and that any\nongoing execution of the work item completes before the cnic_dev is\ndeallocated. Furthermore, since cancel_delayed_work_sync() uses\n__flush_work(work, true) to synchronously wait for any currently\nexecuting instance of the work item to finish, the flush_workqueue()\nbecomes redundant and should be removed.\n\nThis bug was identified through static analysis. To reproduce the issue\nand validate the fix, I simulated the cnic PCI device in QEMU and\nintroduced intentional delays — such as inserting calls to ssleep()\nwithin the cnic_delete_task() function — to increase the likelihood\nof triggering the bug."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ncnic: Corrección de errores de uso después de liberación en cnic_delete_task\n\nEl código original utiliza cancel_delayed_work() en cnic_cm_stop_bnx2x_hw(), lo que no garantiza que el elemento de trabajo retrasado 'delete_task' se haya completado por completo si ya estaba en ejecución. Además, el elemento de trabajo retrasado es cíclico, el flush_workqueue() en cnic_cm_stop_bnx2x_hw() solo bloquea y espera por elementos de trabajo que ya estaban encolados en la cola de trabajo antes de su invocación. Cualquier elemento de trabajo enviado después de que se llama a flush_workqueue() no se incluye en el conjunto de tareas que la operación de vaciado espera. Esto significa que después de que los elementos de trabajo cíclicos hayan terminado de ejecutarse, un elemento de trabajo retrasado aún puede existir en la cola de trabajo. Esto lleva a escenarios de uso después de liberación donde el cnic_dev es desasignado por cnic_free_dev(), mientras delete_task permanece activo e intenta desreferenciar cnic_dev en cnic_delete_task().\n\nUna condición de carrera típica se ilustra a continuación:\n\nCPU 0 (limpieza) | CPU 1 (retrollamada de trabajo retrasado)\ncnic_netdev_event() |\n cnic_stop_hw() | cnic_delete_task()\n cnic_cm_stop_bnx2x_hw() | ...\n cancel_delayed_work() | /* el queue_delayed_work()\n flush_workqueue() | se ejecuta después de flush_workqueue()*/\n | queue_delayed_work()\n cnic_free_dev(dev)//liberar | cnic_delete_task() //nueva instancia\n | dev = cp->dev; //uso\n\nReemplace cancel_delayed_work() con cancel_delayed_work_sync() para asegurar que el elemento de trabajo retrasado cíclico se cancele correctamente y que cualquier ejecución en curso del elemento de trabajo se complete antes de que el cnic_dev sea desasignado. Además, dado que cancel_delayed_work_sync() utiliza __flush_work(work, true) para esperar sincrónicamente a que finalice cualquier instancia en ejecución del elemento de trabajo, el flush_workqueue() se vuelve redundante y debe ser eliminado.\n\nEste error fue identificado mediante análisis estático. Para reproducir el problema y validar la corrección, simulé el dispositivo PCI cnic en QEMU e introduje retrasos intencionales — como insertar llamadas a ssleep() dentro de la función cnic_delete_task() — para aumentar la probabilidad de activar el error."
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