CVE-2026-74481 (GCVE-0-2026-74481)
Vulnerability from cvelistv5
Published
2026-08-15 12:27
Modified
2026-08-19 16:37
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/page_reporting: use system_freezable_wq to fix UAF during suspend During PM freeze (e.g. S3 suspend or S4 hibernation), device drivers like virtio_balloon reset their underlying virtio devices and delete their virtqueues via vdev->config->del_vqs(). However, page reporting work (page_reporting_process) was scheduled on the global system_wq. Because system_wq lacks the WQ_FREEZABLE flag, the PM freezer skips it, leaving page_reporting_process active during suspend. If pages are freed into the buddy allocator while suspending (for example, when core MM invokes the balloon shrinker during S4 hibernation image saving), page reporting triggers virtballoon_free_page_report() on deleted virtqueues, resulting in a Use-After-Free / General Protection Fault: [ 196.795226] general protection fault, probably for non-canonical address 0xaa1436fe70dae6df: 0000 [#1] SMP NOPTI [ 196.825967] Workqueue: events page_reporting_process [ 196.831038] RIP: 0010:virtqueue_add_split+0x233/0x4c0 [virtio_ring] [ 196.927073] virtballoon_free_page_report+0x3a/0xe0 [virtio_balloon] [ 196.946943] page_reporting_process+0x370/0x4f0 Fix this by switching page reporting work to system_freezable_wq. This ensures that the PM freezer pauses page_reporting_process before device drivers destroy their reporting virtqueues. Because the reporting worker is frozen, memory reclamation/freeing (e.g. via shrinker execution) can safely return pages to MM during freeze without triggering unfrozen reporting work on deleted virtqueues. This aligns with the driver's existing design. The comment in virtballoon_freeze() states: /* * The workqueue is already frozen by the PM core before this * function is called. */ Testing: I have verified these fixes using Google’s virtualization infrastructure by running continuous suspend/resume iterations (40+ cycles) while churning memory using stress-ng (`stress-ng --vm 4 --vm-bytes 60% --timeout 1`) to constantly create free pages for the buddy allocator. We also set the `page_reporting_order` parameter to 0 to make the page reporting worker highly sensitive, forcing it to pick up any 4K free pages. This confirmed that the UAF crashes are no longer reproducible.
References
Impacted products
Vendor Product Version
Linux Linux Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
Version: 36e66c554b5c6a9d17a229faca7a61693527b0bd
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{
  "containers": {
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/page_reporting.c"
          ],
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
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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\nmm/page_reporting: use system_freezable_wq to fix UAF during suspend\n\nDuring PM freeze (e.g.  S3 suspend or S4 hibernation), device drivers like\nvirtio_balloon reset their underlying virtio devices and delete their\nvirtqueues via vdev-\u003econfig-\u003edel_vqs().\n\nHowever, page reporting work (page_reporting_process) was scheduled on the\nglobal system_wq.  Because system_wq lacks the WQ_FREEZABLE flag, the PM\nfreezer skips it, leaving page_reporting_process active during suspend.\n\nIf pages are freed into the buddy allocator while suspending (for example,\nwhen core MM invokes the balloon shrinker during S4 hibernation image\nsaving), page reporting triggers virtballoon_free_page_report() on deleted\nvirtqueues, resulting in a Use-After-Free / General Protection Fault:\n\n    [  196.795226] general protection fault, probably for non-canonical address 0xaa1436fe70dae6df: 0000 [#1] SMP NOPTI\n    [  196.825967] Workqueue: events page_reporting_process\n    [  196.831038] RIP: 0010:virtqueue_add_split+0x233/0x4c0 [virtio_ring]\n    [  196.927073] virtballoon_free_page_report+0x3a/0xe0 [virtio_balloon]\n    [  196.946943] page_reporting_process+0x370/0x4f0\n\nFix this by switching page reporting work to system_freezable_wq.  This\nensures that the PM freezer pauses page_reporting_process before device\ndrivers destroy their reporting virtqueues.  Because the reporting worker\nis frozen, memory reclamation/freeing (e.g.  via shrinker execution) can\nsafely return pages to MM during freeze without triggering unfrozen\nreporting work on deleted virtqueues.\n\nThis aligns with the driver\u0027s existing design. The comment in\nvirtballoon_freeze() states:\n    /*\n     * The workqueue is already frozen by the PM core before this\n     * function is called.\n     */\n\nTesting:\nI have verified these fixes using Google\u2019s virtualization infrastructure\nby running continuous suspend/resume iterations (40+ cycles) while\nchurning memory using stress-ng (`stress-ng --vm 4 --vm-bytes 60%\n--timeout 1`) to constantly create free pages for the buddy allocator.  We\nalso set the `page_reporting_order` parameter to 0 to make the page\nreporting worker highly sensitive, forcing it to pick up any 4K free\npages.  This confirmed that the UAF crashes are no longer reproducible."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is reached only through local PM suspend/hibernation and guest memory-free paths (__free_one_page -\u003e page_reporting_notify_free -\u003e page_reporting_process -\u003e virtballoon_free_page_report); it is not reachable via network protocols or remote packet handling.\nAC:L - An attacker with local access can reliably drive the race by churning memory (e.g. stress-ng) to flood page-reporting work while triggering or awaiting S3/S4 suspend, as demonstrated in the fix commit\u0027s reproduction on virtio-balloon VMs.\nPR:L - No real-root capability is required to exercise the memory-free entry path (normal unprivileged mmap/malloc/free syscalls), and many desktop deployments allow session users to initiate suspend via logind/polkit without full init-namespace root.\nUI:N - Exploitation does not require a separate victim action beyond the attacker (or system policy) initiating suspend/hibernation; automated cloud/VM suspend-resume cycles and scripted PM transitions suffice without interactive victim cooperation.\nS:U - Impact is confined to guest kernel memory corruption and crash inside the virtio-balloon/page-reporting subsystem; it does not cross a VM/host, IOMMU, or sandbox security boundary to affect resources outside the kernel\u0027s own authority.\nC:H - This is a kernel heap use-after-free on freed virtqueue metadata accessed through virtqueue_add_split; UAF of kernel objects can be leveraged for arbitrary kernel memory read/info disclosure beyond the observed GPF crash.\nI:H - UAF on virtqueue/vring kernel structures during virtqueue_add_split provides a memory-corruption primitive that can be developed into controlled kernel writes or code execution, not merely a benign crash.\nA:H - The bug provably causes a kernel general protection fault/oops in page_reporting_process during suspend (Workqueue: events), crashing or destabilizing the system and denying availability on every affected suspend/hibernation cycle."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T16:37:36.090Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a4c60046052777ca1dcc83fe3ece2a5136b301f1"
        },
        {
          "url": "https://git.kernel.org/stable/c/b2c094e98f8bb823b3ae475f7169fe2091c40c6d"
        },
        {
          "url": "https://git.kernel.org/stable/c/992f270fd808338fbae1f498a5e325e7e2e20368"
        },
        {
          "url": "https://git.kernel.org/stable/c/f978048326570047e8216e81a67f9c71ef2bb1b1"
        },
        {
          "url": "https://git.kernel.org/stable/c/450f35f4d5a682a0796757e52295df58ddb63bc9"
        },
        {
          "url": "https://git.kernel.org/stable/c/b11907c905fa08eda925395f0724b7a409870f65"
        },
        {
          "url": "https://git.kernel.org/stable/c/faf439b5fa7b231120eac4f7a617e0bfd4f6f5c7"
        },
        {
          "url": "https://git.kernel.org/stable/c/0b45f6927a14914ff685fe0e6f9d11232a1e03df"
        }
      ],
      "title": "mm/page_reporting: use system_freezable_wq to fix UAF during suspend",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74481",
    "datePublished": "2026-08-15T12:27:14.441Z",
    "dateReserved": "2026-08-15T05:44:03.904Z",
    "dateUpdated": "2026-08-19T16:37:36.090Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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