Vulnerability-Lookup

GHSA-4H26-3W83-PFH6

Vulnerability from github – Published: 2026-03-25 12:30 – Updated: 2026-03-25 12:30

Details

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:

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.
bq->count and bq->q[] corruption: concurrent bq_enqueue() modifying bq->count and bq->q[] while bq_xmit_all() is reading them.
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.
__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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-23294"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-03-25T11:16:24Z",
    "severity": null
  },
  "details": "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.",
  "id": "GHSA-4h26-3w83-pfh6",
  "modified": "2026-03-25T12:30:22Z",
  "published": "2026-03-25T12:30:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23294"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1872e75375c40add4a35990de3be77b5741c252c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6c10b019785dc282c5f45d21e4a3f468b8fd6476"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ab1a56c9d99189aa5c6e03940d06e40ba6a28240"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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

Vulnerability from cvelistv5 – Published: 2026-03-25 10:26 – Updated: 2026-03-25 10:26

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 ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/6c10b019785dc282c…
	https://git.kernel.org/stable/c/ab1a56c9d99189aa5…
	https://git.kernel.org/stable/c/1872e75375c40add4…

Impacted products

Vendor

Product

Version

Linux

Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < 6c10b019785dc282c5f45d21e4a3f468b8fd6476 (git)
Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < ab1a56c9d99189aa5c6e03940d06e40ba6a28240 (git)
Affected: 3253cb49cbad4772389d6ef55be75db1f97da910 , < 1872e75375c40add4a35990de3be77b5741c252c (git)

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-rc2 , ≤ * (original_commit_for_fix)

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/devmap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6c10b019785dc282c5f45d21e4a3f468b8fd6476",
              "status": "affected",
              "version": "3253cb49cbad4772389d6ef55be75db1f97da910",
              "versionType": "git"
            },
            {
              "lessThan": "ab1a56c9d99189aa5c6e03940d06e40ba6a28240",
              "status": "affected",
              "version": "3253cb49cbad4772389d6ef55be75db1f97da910",
              "versionType": "git"
            },
            {
              "lessThan": "1872e75375c40add4a35990de3be77b5741c252c",
              "status": "affected",
              "version": "3253cb49cbad4772389d6ef55be75db1f97da910",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/devmap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "lessThan": "6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.17",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.17",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.7",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0-rc2",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-25T10:26:51.946Z",
        "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": "2026-03-25T10:26:51.946Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-4H26-3W83-PFH6

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

Tags

Sightings

Nomenclature