GHSA-HF76-HFQM-MX9Q
Vulnerability from github – Published: 2026-08-15 15:30 – Updated: 2026-08-19 18:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-74481"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T13:17:52Z",
"severity": "HIGH"
},
"details": "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.",
"id": "GHSA-hf76-hfqm-mx9q",
"modified": "2026-08-19T18:32:28Z",
"published": "2026-08-15T15:30:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74481"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0b45f6927a14914ff685fe0e6f9d11232a1e03df"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/450f35f4d5a682a0796757e52295df58ddb63bc9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/992f270fd808338fbae1f498a5e325e7e2e20368"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a4c60046052777ca1dcc83fe3ece2a5136b301f1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b11907c905fa08eda925395f0724b7a409870f65"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b2c094e98f8bb823b3ae475f7169fe2091c40c6d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f978048326570047e8216e81a67f9c71ef2bb1b1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/faf439b5fa7b231120eac4f7a617e0bfd4f6f5c7"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
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Nomenclature
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