CVE-2026-31656 (GCVE-0-2026-31656)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:45 – Updated: 2026-04-24 14:45
VLAI?
Title
drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat A use-after-free / refcount underflow is possible when the heartbeat worker and intel_engine_park_heartbeat() race to release the same engine->heartbeat.systole request. The heartbeat worker reads engine->heartbeat.systole and calls i915_request_put() on it when the request is complete, but clears the pointer in a separate, non-atomic step. Concurrently, a request retirement on another CPU can drop the engine wakeref to zero, triggering __engine_park() -> intel_engine_park_heartbeat(). If the heartbeat timer is pending at that point, cancel_delayed_work() returns true and intel_engine_park_heartbeat() reads the stale non-NULL systole pointer and calls i915_request_put() on it again, causing a refcount underflow: ``` <4> [487.221889] Workqueue: i915-unordered engine_retire [i915] <4> [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0 ... <4> [487.222707] Call Trace: <4> [487.222711] <TASK> <4> [487.222716] intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915] <4> [487.223115] intel_engine_park_heartbeat+0x25/0x40 [i915] <4> [487.223566] __engine_park+0xb9/0x650 [i915] <4> [487.223973] ____intel_wakeref_put_last+0x2e/0xb0 [i915] <4> [487.224408] __intel_wakeref_put_last+0x72/0x90 [i915] <4> [487.224797] intel_context_exit_engine+0x7c/0x80 [i915] <4> [487.225238] intel_context_exit+0xf1/0x1b0 [i915] <4> [487.225695] i915_request_retire.part.0+0x1b9/0x530 [i915] <4> [487.226178] i915_request_retire+0x1c/0x40 [i915] <4> [487.226625] engine_retire+0x122/0x180 [i915] <4> [487.227037] process_one_work+0x239/0x760 <4> [487.227060] worker_thread+0x200/0x3f0 <4> [487.227068] ? __pfx_worker_thread+0x10/0x10 <4> [487.227075] kthread+0x10d/0x150 <4> [487.227083] ? __pfx_kthread+0x10/0x10 <4> [487.227092] ret_from_fork+0x3d4/0x480 <4> [487.227099] ? __pfx_kthread+0x10/0x10 <4> [487.227107] ret_from_fork_asm+0x1a/0x30 <4> [487.227141] </TASK> ``` Fix this by replacing the non-atomic pointer read + separate clear with xchg() in both racing paths. xchg() is a single indivisible hardware instruction that atomically reads the old pointer and writes NULL. This guarantees only one of the two concurrent callers obtains the non-NULL pointer and performs the put, the other gets NULL and skips it. (cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < 70d3e622b10092fc483e28e57b4e8c49d9cc7f68 (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < 8ce44d28a84fd5e053a88b04872a89d95c0779d4 (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < ca3f48c3567dd49efdc55b80029ae74659c682ee (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < a00e92bf6583d019a4fb2c2df7007e6c9b269ce7 (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < 2af8b200cae3fdd0e917ecc2753b28bb40c876c1 (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < 455d98ed527fc94eed90406f90ab2391464ca657 (git)
Affected: 058179e72e0956a2dfe4927db6cbe5fbfb2406aa , < 4c71fd099513bfa8acab529b626e1f0097b76061 (git)
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    Linux Linux Affected: 5.5
Unaffected: 0 , < 5.5 (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.169 , ≤ 6.1.* (semver)
Unaffected: 6.6.135 , ≤ 6.6.* (semver)
Unaffected: 6.12.82 , ≤ 6.12.* (semver)
Unaffected: 6.18.23 , ≤ 6.18.* (semver)
Unaffected: 6.19.13 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c"
          ],
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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            },
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              "version": "5.15.203",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.1.169",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.6.135",
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              "status": "unaffected",
              "version": "6.12.82",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.23",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
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                  "vulnerable": true
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                  "versionEndExcluding": "6.1.169",
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat\n\nA use-after-free / refcount underflow is possible when the heartbeat\nworker and intel_engine_park_heartbeat() race to release the same\nengine-\u003eheartbeat.systole request.\n\nThe heartbeat worker reads engine-\u003eheartbeat.systole and calls\ni915_request_put() on it when the request is complete, but clears\nthe pointer in a separate, non-atomic step. Concurrently, a request\nretirement on another CPU can drop the engine wakeref to zero, triggering\n__engine_park() -\u003e intel_engine_park_heartbeat(). If the heartbeat\ntimer is pending at that point, cancel_delayed_work() returns true and\nintel_engine_park_heartbeat() reads the stale non-NULL systole pointer\nand calls i915_request_put() on it again, causing a refcount underflow:\n\n```\n\u003c4\u003e [487.221889] Workqueue: i915-unordered engine_retire [i915]\n\u003c4\u003e [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\n...\n\u003c4\u003e [487.222707] Call Trace:\n\u003c4\u003e [487.222711]  \u003cTASK\u003e\n\u003c4\u003e [487.222716]  intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\n\u003c4\u003e [487.223115]  intel_engine_park_heartbeat+0x25/0x40 [i915]\n\u003c4\u003e [487.223566]  __engine_park+0xb9/0x650 [i915]\n\u003c4\u003e [487.223973]  ____intel_wakeref_put_last+0x2e/0xb0 [i915]\n\u003c4\u003e [487.224408]  __intel_wakeref_put_last+0x72/0x90 [i915]\n\u003c4\u003e [487.224797]  intel_context_exit_engine+0x7c/0x80 [i915]\n\u003c4\u003e [487.225238]  intel_context_exit+0xf1/0x1b0 [i915]\n\u003c4\u003e [487.225695]  i915_request_retire.part.0+0x1b9/0x530 [i915]\n\u003c4\u003e [487.226178]  i915_request_retire+0x1c/0x40 [i915]\n\u003c4\u003e [487.226625]  engine_retire+0x122/0x180 [i915]\n\u003c4\u003e [487.227037]  process_one_work+0x239/0x760\n\u003c4\u003e [487.227060]  worker_thread+0x200/0x3f0\n\u003c4\u003e [487.227068]  ? __pfx_worker_thread+0x10/0x10\n\u003c4\u003e [487.227075]  kthread+0x10d/0x150\n\u003c4\u003e [487.227083]  ? __pfx_kthread+0x10/0x10\n\u003c4\u003e [487.227092]  ret_from_fork+0x3d4/0x480\n\u003c4\u003e [487.227099]  ? __pfx_kthread+0x10/0x10\n\u003c4\u003e [487.227107]  ret_from_fork_asm+0x1a/0x30\n\u003c4\u003e [487.227141]  \u003c/TASK\u003e\n```\n\nFix this by replacing the non-atomic pointer read + separate clear with\nxchg() in both racing paths. xchg() is a single indivisible hardware\ninstruction that atomically reads the old pointer and writes NULL. This\nguarantees only one of the two concurrent callers obtains the non-NULL\npointer and performs the put, the other gets NULL and skips it.\n\n(cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-24T14:45:07.738Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/70d3e622b10092fc483e28e57b4e8c49d9cc7f68"
        },
        {
          "url": "https://git.kernel.org/stable/c/8ce44d28a84fd5e053a88b04872a89d95c0779d4"
        },
        {
          "url": "https://git.kernel.org/stable/c/ca3f48c3567dd49efdc55b80029ae74659c682ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/a00e92bf6583d019a4fb2c2df7007e6c9b269ce7"
        },
        {
          "url": "https://git.kernel.org/stable/c/2af8b200cae3fdd0e917ecc2753b28bb40c876c1"
        },
        {
          "url": "https://git.kernel.org/stable/c/455d98ed527fc94eed90406f90ab2391464ca657"
        },
        {
          "url": "https://git.kernel.org/stable/c/4c71fd099513bfa8acab529b626e1f0097b76061"
        }
      ],
      "title": "drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31656",
    "datePublished": "2026-04-24T14:45:07.738Z",
    "dateReserved": "2026-03-09T15:48:24.129Z",
    "dateUpdated": "2026-04-24T14:45:07.738Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31656",
      "date": "2026-04-25",
      "epss": "0.00024",
      "percentile": "0.06802"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31656\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-24T15:16:45.097\",\"lastModified\":\"2026-04-24T17:51:40.810\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ndrm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat\\n\\nA use-after-free / refcount underflow is possible when the heartbeat\\nworker and intel_engine_park_heartbeat() race to release the same\\nengine-\u003eheartbeat.systole request.\\n\\nThe heartbeat worker reads engine-\u003eheartbeat.systole and calls\\ni915_request_put() on it when the request is complete, but clears\\nthe pointer in a separate, non-atomic step. Concurrently, a request\\nretirement on another CPU can drop the engine wakeref to zero, triggering\\n__engine_park() -\u003e intel_engine_park_heartbeat(). If the heartbeat\\ntimer is pending at that point, cancel_delayed_work() returns true and\\nintel_engine_park_heartbeat() reads the stale non-NULL systole pointer\\nand calls i915_request_put() on it again, causing a refcount underflow:\\n\\n```\\n\u003c4\u003e [487.221889] Workqueue: i915-unordered engine_retire [i915]\\n\u003c4\u003e [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\\n...\\n\u003c4\u003e [487.222707] Call Trace:\\n\u003c4\u003e [487.222711]  \u003cTASK\u003e\\n\u003c4\u003e [487.222716]  intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\\n\u003c4\u003e [487.223115]  intel_engine_park_heartbeat+0x25/0x40 [i915]\\n\u003c4\u003e [487.223566]  __engine_park+0xb9/0x650 [i915]\\n\u003c4\u003e [487.223973]  ____intel_wakeref_put_last+0x2e/0xb0 [i915]\\n\u003c4\u003e [487.224408]  __intel_wakeref_put_last+0x72/0x90 [i915]\\n\u003c4\u003e [487.224797]  intel_context_exit_engine+0x7c/0x80 [i915]\\n\u003c4\u003e [487.225238]  intel_context_exit+0xf1/0x1b0 [i915]\\n\u003c4\u003e [487.225695]  i915_request_retire.part.0+0x1b9/0x530 [i915]\\n\u003c4\u003e [487.226178]  i915_request_retire+0x1c/0x40 [i915]\\n\u003c4\u003e [487.226625]  engine_retire+0x122/0x180 [i915]\\n\u003c4\u003e [487.227037]  process_one_work+0x239/0x760\\n\u003c4\u003e [487.227060]  worker_thread+0x200/0x3f0\\n\u003c4\u003e [487.227068]  ? __pfx_worker_thread+0x10/0x10\\n\u003c4\u003e [487.227075]  kthread+0x10d/0x150\\n\u003c4\u003e [487.227083]  ? __pfx_kthread+0x10/0x10\\n\u003c4\u003e [487.227092]  ret_from_fork+0x3d4/0x480\\n\u003c4\u003e [487.227099]  ? __pfx_kthread+0x10/0x10\\n\u003c4\u003e [487.227107]  ret_from_fork_asm+0x1a/0x30\\n\u003c4\u003e [487.227141]  \u003c/TASK\u003e\\n```\\n\\nFix this by replacing the non-atomic pointer read + separate clear with\\nxchg() in both racing paths. xchg() is a single indivisible hardware\\ninstruction that atomically reads the old pointer and writes NULL. This\\nguarantees only one of the two concurrent callers obtains the non-NULL\\npointer and performs the put, the other gets NULL and skips it.\\n\\n(cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2af8b200cae3fdd0e917ecc2753b28bb40c876c1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/455d98ed527fc94eed90406f90ab2391464ca657\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4c71fd099513bfa8acab529b626e1f0097b76061\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/70d3e622b10092fc483e28e57b4e8c49d9cc7f68\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8ce44d28a84fd5e053a88b04872a89d95c0779d4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a00e92bf6583d019a4fb2c2df7007e6c9b269ce7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ca3f48c3567dd49efdc55b80029ae74659c682ee\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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