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mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch() migrate_pages_batch() unmaps each folio before moving it, and every unmap runs the mmu_notifier invalidate callbacks. On KVM hosts try_to_migrate() ends up in kvm_mmu_notifier_invalidate_range_start() -> tdp_mmu_zap_leafs(), which is expensive, so unmapping a large batch keeps the CPU busy for a long time. The loop already calls cond_resched(), but on PREEMPTION kernels that is a no-op, and involuntary preemption is not a Tasks-RCU quiescent state. A long batch therefore never reports a quiescent state, and the migrating task (e.g. kcompactd) becomes a Tasks-RCU holdout, stalling the Tasks-RCU grace period for minutes, which is common at Meta fleet: INFO: rcu_tasks detected stalls on tasks: 0000000055349ecc: .. nvcsw: 1157401/1157401 holdout: 1 idle_cpu: -1/56 task:kcompactd0 state:R running task Call Trace: tdp_mmu_zap_leafs tdp_mmu_next_root gfn_to_pfn_cache_invalidate_start kvm_mmu_notifier_invalidate_range_start __mmu_notifier_invalidate_range_start try_to_migrate_one try_to_migrate migrate_pages_batch migrate_pages compact_zone compact_node kcompactd kthread Use cond_resched_tasks_rcu_qs() so a quiescent state is reported even when cond_resched() does nothing. This has also been discussed at [1]

Announced Source revision 1
Original source ↗

CVE-2026-89756

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-89756

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "8c6d63d434ebb85c6cf3dac1e70a171b183c6614",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "4757542649af56d894e25e30f57cd497dffad53f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "4996a7bc01ef35570664854dac2530c604981039",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "5dc0daff0341c6baba19c38f47d299ac831d7e99",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "66734981b4d3c105223a13c827c9c73be18d91ad",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8315f42295d2667a7f942f154b73a86fd7cb2227",
        "lessThan": "efe8f86c0916f0f74eea74ae21a3b37f728c6bad",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "mm/migrate.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "3.18"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "3.18",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.1.188",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.157",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.109",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.50",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.4",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "mm/migrate.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89756

Source reference: /cveMetadata/cveId

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Event
#35229 · Revision 1
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