CVE-2026-23294 (GCVE-0-2026-23294)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:26 – Updated: 2026-05-11 22:04
VLAI?
Title
bpf: Fix race in devmap on PREEMPT_RT
Summary
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. This leads to several races: 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. The race between task A (__dev_flush -> bq_xmit_all) and task B (bq_enqueue -> bq_xmit_all) on the same CPU: 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! */ 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.
Severity ?
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < 6c10b019785dc282c5f45d21e4a3f468b8fd6476 (git)
Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < ab1a56c9d99189aa5c6e03940d06e40ba6a28240 (git)
Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < 1872e75375c40add4a35990de3be77b5741c252c (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/devmap.c"
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          "vendor": "Linux",
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              "version": "6.18"
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              "versionType": "semver"
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        }
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "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-\u003eq[]: bq_xmit_all() snapshots\n   cnt = bq-\u003ecount, then iterates bq-\u003eq[0..cnt-1] to transmit frames.\n   If preempted after the snapshot, a second task can call bq_enqueue()\n   -\u003e 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-\u003eq[], causing use-after-free.\n\n2. bq-\u003ecount and bq-\u003eq[] corruption: concurrent bq_enqueue() modifying\n   bq-\u003ecount and bq-\u003eq[] while bq_xmit_all() is reading them.\n\n3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq-\u003edev_rx and\n   bq-\u003exdp_prog after bq_xmit_all(). If preempted between\n   bq_xmit_all() return and bq-\u003edev_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 -\u003e bq_xmit_all) and task B\n(bq_enqueue -\u003e 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-\u003ecount  /* e.g. 16 */\n      /* start iterating bq-\u003eq[] */\n    \u003c-- CFS preempts Task A --\u003e\n                                   bq_enqueue(dev, xdpf)\n                                     bq-\u003ecount == DEV_MAP_BULK_SIZE\n                                     bq_xmit_all(bq, 0)\n                                       cnt = bq-\u003ecount  /* same 16! */\n                                       ndo_xdp_xmit(bq-\u003eq[])\n                                       /* frames freed by driver */\n                                       bq-\u003ecount = 0\n    \u003c-- Task A resumes --\u003e\n      ndo_xdp_xmit(bq-\u003eq[])\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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:04:06.077Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6c10b019785dc282c5f45d21e4a3f468b8fd6476"
        },
        {
          "url": "https://git.kernel.org/stable/c/ab1a56c9d99189aa5c6e03940d06e40ba6a28240"
        },
        {
          "url": "https://git.kernel.org/stable/c/1872e75375c40add4a35990de3be77b5741c252c"
        }
      ],
      "title": "bpf: Fix race in devmap on PREEMPT_RT",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23294",
    "datePublished": "2026-03-25T10:26:51.946Z",
    "dateReserved": "2026-01-13T15:37:45.993Z",
    "dateUpdated": "2026-05-11T22:04:06.077Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-23294",
      "date": "2026-05-17",
      "epss": "0.00015",
      "percentile": "0.03328"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23294\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-25T11:16:24.697\",\"lastModified\":\"2026-04-02T15:16:30.507\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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-\u003eq[]: bq_xmit_all() snapshots\\n   cnt = bq-\u003ecount, then iterates bq-\u003eq[0..cnt-1] to transmit frames.\\n   If preempted after the snapshot, a second task can call bq_enqueue()\\n   -\u003e 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-\u003eq[], causing use-after-free.\\n\\n2. bq-\u003ecount and bq-\u003eq[] corruption: concurrent bq_enqueue() modifying\\n   bq-\u003ecount and bq-\u003eq[] while bq_xmit_all() is reading them.\\n\\n3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq-\u003edev_rx and\\n   bq-\u003exdp_prog after bq_xmit_all(). If preempted between\\n   bq_xmit_all() return and bq-\u003edev_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 -\u003e bq_xmit_all) and task B\\n(bq_enqueue -\u003e 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-\u003ecount  /* e.g. 16 */\\n      /* start iterating bq-\u003eq[] */\\n    \u003c-- CFS preempts Task A --\u003e\\n                                   bq_enqueue(dev, xdpf)\\n                                     bq-\u003ecount == DEV_MAP_BULK_SIZE\\n                                     bq_xmit_all(bq, 0)\\n                                       cnt = bq-\u003ecount  /* same 16! */\\n                                       ndo_xdp_xmit(bq-\u003eq[])\\n                                       /* frames freed by driver */\\n                                       bq-\u003ecount = 0\\n    \u003c-- Task A resumes --\u003e\\n      ndo_xdp_xmit(bq-\u003eq[])\\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 condici\u00f3n 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 m\u00faltiples tareas preemptivas en la misma CPU.\\n\\nEl c\u00f3digo original asume que bq_enqueue() y __dev_flush() se ejecutan at\u00f3micamente con respecto la una a la otra en la misma CPU, confiando en local_bh_disable() para prevenir la expropiaci\u00f3n. Sin embargo, en PREEMPT_RT, local_bh_disable() solo llama a migrate_disable() (cuando PREEMPT_RT_NEEDS_BH_LOCK no est\u00e1 configurado) y no deshabilita la expropiaci\u00f3n, lo que permite que la planificaci\u00f3n 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 liberaci\u00f3n / uso despu\u00e9s de liberaci\u00f3n en bq-\u0026gt;q[]: bq_xmit_all() toma una instant\u00e1nea de cnt = bq-\u0026gt;count, luego itera bq-\u0026gt;q[0..cnt-1] para transmitir tramas. Si es expropiada despu\u00e9s de la instant\u00e1nea, una segunda tarea puede llamar a bq_enqueue() -\u0026gt; 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-\u0026gt;q[], causando uso despu\u00e9s de liberaci\u00f3n.\\n\\n2. Corrupci\u00f3n de bq-\u0026gt;count y bq-\u0026gt;q[]: bq_enqueue() concurrente modificando bq-\u0026gt;count y bq-\u0026gt;q[] mientras bq_xmit_all() los est\u00e1 leyendo.\\n\\n3. Condici\u00f3n de carrera de desmontaje de dev_rx/xdp_prog: __dev_flush() borra bq-\u0026gt;dev_rx y bq-\u0026gt;xdp_prog despu\u00e9s de bq_xmit_all(). Si es expropiada entre el retorno de bq_xmit_all() y bq-\u0026gt;dev_rx = NULL, una bq_enqueue() expropiadora ve dev_rx a\u00fan configurado (no-NULL), omite a\u00f1adir 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 hu\u00e9rfana la trama reci\u00e9n encolada.\\n\\n4. __list_del_clearprev() en flush_node: similar a la condici\u00f3n 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 condici\u00f3n de carrera entre la tarea A (__dev_flush -\u0026gt; bq_xmit_all) y la tarea B (bq_enqueue -\u0026gt; bq_xmit_all) en la misma CPU:\\n\\n  Tarea A (xdp_do_flush)          Tarea B (redirecci\u00f3n ndo_xdp_xmit)\\n  ----------------------         --------------------------------\\n  __dev_flush(flush_list)\\n    bq_xmit_all(bq)\\n      cnt = bq-\u0026gt;count  /* ej. 16 */\\n      /* comienza a iterar bq-\u0026gt;q[] */\\n    \u0026lt;-- CFS expropia la Tarea A --\u0026gt;\\n                                   bq_enqueue(dev, xdpf)\\n                                     bq-\u0026gt;count == DEV_MAP_BULK_SIZE\\n                                     bq_xmit_all(bq, 0)\\n                                       cnt = bq-\u0026gt;count  /* \u00a1los mismos 16! */\\n                                       ndo_xdp_xmit(bq-\u0026gt;q[])\\n                                       /* tramas liberadas por el controlador */\\n                                       bq-\u0026gt;count = 0\\n    \u0026lt;-- La Tarea A se reanuda --\u0026gt;\\n      ndo_xdp_xmit(bq-\u0026gt;q[])\\n      /* uso despu\u00e9s de liberaci\u00f3n: \u00a1tramas ya liberadas! */\\n\\nSolucione esto a\u00f1adiendo un local_lock_t a xdp_dev_bulk_queue y adquiri\u00e9ndolo en bq_enqueue() y __dev_flush(). Estas rutas ya se ejecutan bajo local_bh_disable(), as\u00ed que use local_lock_nested_bh() que en no-RT es una anotaci\u00f3n pura sin sobrecarga, y en PREEMPT_RT proporciona un bloqueo de suspensi\u00f3n por CPU que serializa el acceso a la bq.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.0,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.0,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1872e75375c40add4a35990de3be77b5741c252c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6c10b019785dc282c5f45d21e4a3f468b8fd6476\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ab1a56c9d99189aa5c6e03940d06e40ba6a28240\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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