CVE-2026-23294
Estado: AnalizadaAlta (7)—
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix race in devmap on PREEMPT_RT
On PREEMPT_RT kernels, the per-CPU xdp_dev_bulk_queue (bq) can be accessed concurrently by multiple preemptible tasks on the same CPU.
The original code assumes bq_enqueue() and __dev_flush() run atomically with respect to each other on the same CPU, relying on local_bh_disable() to prevent preemption. However, on PREEMPT_RT, local_bh_disable() only calls migrate_disable() (when PREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable preemption, which allows CFS scheduling to preempt a task during bq_xmit_all(), enabling another task on the same CPU to enter bq_enqueue() and operate on the same per-CPU bq concurrently.
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This leads to several races:
The race between task A (__dev_flush -> bq_xmit_all) and task B (bq_enqueue -> bq_xmit_all) on the same CPU:
Fix this by adding a local_lock_t to xdp_dev_bulk_queue and acquiring it in bq_enqueue() and __dev_flush(). These paths already run under local_bh_disable(), so use local_lock_nested_bh() which on non-RT is a pure annotation with no overhead, and on PREEMPT_RT provides a per-CPU sleeping lock that serializes access to the bq.
Detalles técnicos trazas, registros y código del informe original
1. Double-free / use-after-free on bq->q[]: bq_xmit_all() snapshots
cnt = bq->count, then iterates bq->q[0..cnt-1] to transmit frames.
If preempted after the snapshot, a second task can call bq_enqueue()
-> bq_xmit_all() on the same bq, transmitting (and freeing) the
same frames. When the first task resumes, it operates on stale
pointers in bq->q[], causing use-after-free.
2. bq->count and bq->q[] corruption: concurrent bq_enqueue() modifying
bq->count and bq->q[] while bq_xmit_all() is reading them.
3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq->dev_rx and
bq->xdp_prog after bq_xmit_all(). If preempted between
bq_xmit_all() return and bq->dev_rx = NULL, a preempting
bq_enqueue() sees dev_rx still set (non-NULL), skips adding bq to
the flush_list, and enqueues a frame. When __dev_flush() resumes,
it clears dev_rx and removes bq from the flush_list, orphaning the
newly enqueued frame.
4. __list_del_clearprev() on flush_node: similar to the cpumap race,
both tasks can call __list_del_clearprev() on the same flush_node,
the second dereferences the prev pointer already set to NULL.
Task A (xdp_do_flush) Task B (ndo_xdp_xmit redirect)
---------------------- --------------------------------
__dev_flush(flush_list)
bq_xmit_all(bq)
cnt = bq->count /* e.g. 16 */
/* start iterating bq->q[] */
<-- CFS preempts Task A -->
bq_enqueue(dev, xdpf)
bq->count == DEV_MAP_BULK_SIZE
bq_xmit_all(bq, 0)
cnt = bq->count /* same 16! */
ndo_xdp_xmit(bq->q[])
/* frames freed by driver */
bq->count = 0
<-- Task A resumes -->
ndo_xdp_xmit(bq->q[])
/* use-after-free: frames already freed! */CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.09%
- Percentil entre todas las CVEs puntuadas: 0
- Fecha de la puntuación: 4/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation75 % - Impacto secundario
T1499.004Application or System Exploitationimpact65 %
Race condition en kernel Linux con acceso local y privilegios limitados (PR:L) permite escalada via corrupción de memoria en devmap; impacto DoS por uso-after-free y corrupción.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
CWE
- CWE-362
Referencias
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix race in devmap on PREEMPT_RT\n\nOn PREEMPT_RT kernels, the per-CPU xdp_dev_bulk_queue (bq) can be\naccessed concurrently by multiple preemptible tasks on the same CPU.\n\nThe original code assumes bq_enqueue() and __dev_flush() run atomically\nwith respect to each other on the same CPU, relying on\nlocal_bh_disable() to prevent preemption. However, on PREEMPT_RT,\nlocal_bh_disable() only calls migrate_disable() (when\nPREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable\npreemption, which allows CFS scheduling to preempt a task during\nbq_xmit_all(), enabling another task on the same CPU to enter\nbq_enqueue() and operate on the same per-CPU bq concurrently.\n\nThis leads to several races:\n\n1. Double-free / use-after-free on bq->q[]: bq_xmit_all() snapshots\n cnt = bq->count, then iterates bq->q[0..cnt-1] to transmit frames.\n If preempted after the snapshot, a second task can call bq_enqueue()\n -> bq_xmit_all() on the same bq, transmitting (and freeing) the\n same frames. When the first task resumes, it operates on stale\n pointers in bq->q[], causing use-after-free.\n\n2. bq->count and bq->q[] corruption: concurrent bq_enqueue() modifying\n bq->count and bq->q[] while bq_xmit_all() is reading them.\n\n3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq->dev_rx and\n bq->xdp_prog after bq_xmit_all(). If preempted between\n bq_xmit_all() return and bq->dev_rx = NULL, a preempting\n bq_enqueue() sees dev_rx still set (non-NULL), skips adding bq to\n the flush_list, and enqueues a frame. When __dev_flush() resumes,\n it clears dev_rx and removes bq from the flush_list, orphaning the\n newly enqueued frame.\n\n4. __list_del_clearprev() on flush_node: similar to the cpumap race,\n both tasks can call __list_del_clearprev() on the same flush_node,\n the second dereferences the prev pointer already set to NULL.\n\nThe race between task A (__dev_flush -> bq_xmit_all) and task B\n(bq_enqueue -> bq_xmit_all) on the same CPU:\n\n Task A (xdp_do_flush) Task B (ndo_xdp_xmit redirect)\n ---------------------- --------------------------------\n __dev_flush(flush_list)\n bq_xmit_all(bq)\n cnt = bq->count /* e.g. 16 */\n /* start iterating bq->q[] */\n <-- CFS preempts Task A -->\n bq_enqueue(dev, xdpf)\n bq->count == DEV_MAP_BULK_SIZE\n bq_xmit_all(bq, 0)\n cnt = bq->count /* same 16! */\n ndo_xdp_xmit(bq->q[])\n /* frames freed by driver */\n bq->count = 0\n <-- Task A resumes -->\n ndo_xdp_xmit(bq->q[])\n /* use-after-free: frames already freed! */\n\nFix this by adding a local_lock_t to xdp_dev_bulk_queue and acquiring\nit in bq_enqueue() and __dev_flush(). These paths already run under\nlocal_bh_disable(), so use local_lock_nested_bh() which on non-RT is\na pure annotation with no overhead, and on PREEMPT_RT provides a\nper-CPU sleeping lock that serializes access to the bq."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbpf: Corrige condición de carrera en devmap en PREEMPT_RT\n\nEn kernels PREEMPT_RT, la xdp_dev_bulk_queue (bq) por CPU puede ser accedida concurrentemente por múltiples tareas preemptivas en la misma CPU.\n\nEl código original asume que bq_enqueue() y __dev_flush() se ejecutan atómicamente con respecto la una a la otra en la misma CPU, confiando en local_bh_disable() para prevenir la expropiación. Sin embargo, en PREEMPT_RT, local_bh_disable() solo llama a migrate_disable() (cuando PREEMPT_RT_NEEDS_BH_LOCK no está configurado) y no deshabilita la expropiación, lo que permite que la planificación CFS expropie una tarea durante bq_xmit_all(), permitiendo que otra tarea en la misma CPU entre en bq_enqueue() y opere en la misma bq por CPU concurrentemente.\n\nEsto lleva a varias condiciones de carrera:\n\n1. Doble liberación / uso después de liberación en bq->q[]: bq_xmit_all() toma una instantánea de cnt = bq->count, luego itera bq->q[0..cnt-1] para transmitir tramas. Si es expropiada después de la instantánea, una segunda tarea puede llamar a bq_enqueue() -> bq_xmit_all() en la misma bq, transmitiendo (y liberando) las mismas tramas. Cuando la primera tarea se reanuda, opera con punteros obsoletos en bq->q[], causando uso después de liberación.\n\n2. Corrupción de bq->count y bq->q[]: bq_enqueue() concurrente modificando bq->count y bq->q[] mientras bq_xmit_all() los está leyendo.\n\n3. Condición de carrera de desmontaje de dev_rx/xdp_prog: __dev_flush() borra bq->dev_rx y bq->xdp_prog después de bq_xmit_all(). Si es expropiada entre el retorno de bq_xmit_all() y bq->dev_rx = NULL, una bq_enqueue() expropiadora ve dev_rx aún configurado (no-NULL), omite añadir bq a la flush_list, y encola una trama. Cuando __dev_flush() se reanuda, borra dev_rx y elimina bq de la flush_list, dejando huérfana la trama recién encolada.\n\n4. __list_del_clearprev() en flush_node: similar a la condición de carrera de cpumap, ambas tareas pueden llamar a __list_del_clearprev() en el mismo flush_node, la segunda desreferencia el puntero prev ya establecido en NULL.\n\nLa condición de carrera entre la tarea A (__dev_flush -> bq_xmit_all) y la tarea B (bq_enqueue -> bq_xmit_all) en la misma CPU:\n\n Tarea A (xdp_do_flush) Tarea B (redirección ndo_xdp_xmit)\n ---------------------- --------------------------------\n __dev_flush(flush_list)\n bq_xmit_all(bq)\n cnt = bq->count /* ej. 16 */\n /* comienza a iterar bq->q[] */\n <-- CFS expropia la Tarea A -->\n bq_enqueue(dev, xdpf)\n bq->count == DEV_MAP_BULK_SIZE\n bq_xmit_all(bq, 0)\n cnt = bq->count /* ¡los mismos 16! */\n ndo_xdp_xmit(bq->q[])\n /* tramas liberadas por el controlador */\n bq->count = 0\n <-- La Tarea A se reanuda -->\n ndo_xdp_xmit(bq->q[])\n /* uso después de liberación: ¡tramas ya liberadas! */\n\nSolucione esto añadiendo un local_lock_t a xdp_dev_bulk_queue y adquiriéndolo en bq_enqueue() y __dev_flush(). Estas rutas ya se ejecutan bajo local_bh_disable(), así que use local_lock_nested_bh() que en no-RT es una anotación pura sin sobrecarga, y en PREEMPT_RT proporciona un bloqueo de suspensión por CPU que serializa el acceso a la bq."
}
],
"lastModified": "2026-06-17T10:21:16.460",
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