{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2"
            },
            {
              "fixed": "4996a7bc01ef35570664854dac2530c604981039"
            },
            {
              "fixed": "5dc0daff0341c6baba19c38f47d299ac831d7e99"
            },
            {
              "fixed": "66734981b4d3c105223a13c827c9c73be18d91ad"
            },
            {
              "fixed": "efe8f86c0916f0f74eea74ae21a3b37f728c6bad"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.109"
            },
            {
              "fixed": "6.18.50"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.109"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.50"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89756.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()\n\nmigrate_pages_batch() unmaps each folio before moving it, and every\nunmap runs the mmu_notifier invalidate callbacks.  On KVM hosts\ntry_to_migrate() ends up in kvm_mmu_notifier_invalidate_range_start() -\u003e\ntdp_mmu_zap_leafs(), which is expensive, so unmapping a large batch keeps\nthe CPU busy for a long time.\n\nThe loop already calls cond_resched(), but on PREEMPTION kernels that is\na no-op, and involuntary preemption is not a Tasks-RCU quiescent state.\n\nA long batch therefore never reports a quiescent state, and the\nmigrating task (e.g. kcompactd) becomes a Tasks-RCU holdout, stalling the\nTasks-RCU grace period for minutes, which is common at Meta fleet:\n\n  INFO: rcu_tasks detected stalls on tasks:\n  0000000055349ecc: .. nvcsw: 1157401/1157401 holdout: 1 idle_cpu: -1/56 task:kcompactd0      state:R  running task\n  Call Trace:\n   tdp_mmu_zap_leafs\n   tdp_mmu_next_root\n   gfn_to_pfn_cache_invalidate_start\n   kvm_mmu_notifier_invalidate_range_start\n   __mmu_notifier_invalidate_range_start\n   try_to_migrate_one\n   try_to_migrate\n   migrate_pages_batch\n   migrate_pages\n   compact_zone\n   compact_node\n   kcompactd\n   kthread\n\nUse cond_resched_tasks_rcu_qs() so a quiescent state is reported even\nwhen cond_resched() does nothing.\n\nThis has also been discussed at [1]",
  "id": "CVE-2026-89756",
  "modified": "2026-09-13T03:30:51.969900912Z",
  "published": "2026-09-11T19:46:59.093Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4996a7bc01ef35570664854dac2530c604981039"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5dc0daff0341c6baba19c38f47d299ac831d7e99"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/66734981b4d3c105223a13c827c9c73be18d91ad"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/efe8f86c0916f0f74eea74ae21a3b37f728c6bad"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89756.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89756"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()"
}