CVE-2026-89986 (GCVE-0-2026-89986)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-10-19 08:56
VLAI
Title
mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave() syzbot reported a sleeping function called from invalid context splat in bucket_table_alloc(). When rhashtable_insert_slow() rehashes the table under rcu_read_lock(), it calls bucket_table_alloc(..., GFP_ATOMIC | __GFP_NOWARN). If the bucket table allocation uses vmalloc, __vmalloc_node_range_noprof() invokes vm_area_alloc_pages() -> alloc_pages_bulk_mempolicy_noprof() with the passed GFP_ATOMIC flags. If the current task has an MPOL_WEIGHTED_INTERLEAVE mempolicy, alloc_pages_bulk_weighted_interleave() is called and currently hardcodes GFP_KERNEL when allocating the temporary weights array, triggering a might_alloc() splat in atomic/RCU contexts. Pass the gfp flags (masked with GFP_RECLAIM_MASK to strip page-allocator zone modifiers like __GFP_HIGHMEM) received by alloc_pages_bulk_weighted_interleave() to kmalloc() instead of hardcoding GFP_KERNEL. Since the weights buffer is immediately initialized in full, kmalloc() is sufficient.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6649 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: fa3bea4e1f8202d787709b7e3654eb0a99aed758 , < bcb3d0c867ee40dc48e9c085bf328fbc679b6656 (git)
Affected: fa3bea4e1f8202d787709b7e3654eb0a99aed758 , < 0ceda28f371df9e0bbdaa29214f71fe8298f23d8 (git)
Affected: fa3bea4e1f8202d787709b7e3654eb0a99aed758 , < 2943f1f4b7f2816177060eb9f551f2e6d8b629ba (git)
Affected: fa3bea4e1f8202d787709b7e3654eb0a99aed758 , < 540e583b66d6402bf556fde5e53c817a54c1afe5 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.12.110 , ≤ 6.12.* (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()\n\nsyzbot reported a sleeping function called from invalid context splat in\nbucket_table_alloc().\n\nWhen rhashtable_insert_slow() rehashes the table under rcu_read_lock(), it\ncalls bucket_table_alloc(..., GFP_ATOMIC | __GFP_NOWARN).  If the bucket\ntable allocation uses vmalloc, __vmalloc_node_range_noprof() invokes\nvm_area_alloc_pages() -\u003e alloc_pages_bulk_mempolicy_noprof() with the\npassed GFP_ATOMIC flags.\n\nIf the current task has an MPOL_WEIGHTED_INTERLEAVE mempolicy,\nalloc_pages_bulk_weighted_interleave() is called and currently hardcodes\nGFP_KERNEL when allocating the temporary weights array, triggering a\nmight_alloc() splat in atomic/RCU contexts.\n\nPass the gfp flags (masked with GFP_RECLAIM_MASK to strip page-allocator\nzone modifiers like __GFP_HIGHMEM) received by\nalloc_pages_bulk_weighted_interleave() to kmalloc() instead of hardcoding\nGFP_KERNEL.  Since the weights buffer is immediately initialized in full,\nkmalloc() is sufficient."
        }
      ],
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            "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"
          },
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              "value": "AV:L - Triggering requires set_mempolicy(MPOL_WEIGHTED_INTERLEAVE) on the attacker\u0027s task and a local syscall that grows an rhashtable until GFP_ATOMIC kvmalloc falls back to vmalloc (nftables hash sets, tc flower, BPF rhashtable maps); softirq/packet paths use default_policy via in_interrupt() and cannot apply the attacker\u0027s mempolicy.\nAC:L - The attacker fully controls setup: set_mempolicy on their own task, insert enough rhashtable elements for a \u003ePAGE_SIZE bucket table, and apply memory pressure so GFP_ATOMIC kmalloc fails and kvmalloc uses vmalloc; CONFIG_NUMA is standard on x86_64/arm64 distro and cloud kernels, and no attacker-uncontrollable race is required.\nPR:L - set_mempolicy() has no capability check, and the rhashtable rehash path is reachable by an unprivileged user via nftables or tc in a user+net namespace where CAP_NET_ADMIN is namespace-local; init-namespace root is not required.\nUI:N - The attacker sets their own mempolicy and drives the rhashtable inserts themselves; no victim action such as mounting a filesystem or opening a file is required.\nS:U - The illegal GFP_KERNEL allocation and any resulting RCU use-after-free of the rhashtable bucket table stay inside the host kernel\u0027s memory-management authority; this is standard in-kernel impact, not a VM, IOMMU, or sandbox boundary crossing.\nC:H - Sleeping under rcu_read_lock() in rhashtable_insert_slow() on non-PREEMPT_RCU kernels can let the grace period complete and free the old bucket table before rhashtable_rehash_attach() uses it, yielding a use-after-free read of kernel heap.\nI:H - The same RCU-break UAF lets rhashtable_rehash_attach() cmpxchg old_tbl-\u003efuture_tbl on a freed table, which is an attacker-sprayable kernel write primitive via heap reuse rather than a clean failure.\nA:H - GFP_KERNEL under rcu_read_lock produces a sleeping-from-invalid-context BUG/WARN (panic with panic_on_warn), can RCU-stall or deadlock if reclaim actually sleeps, and the bucket-table UAF can oops the kernel."
            }
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        "dateUpdated": "2026-10-19T08:56:00.678Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/540e583b66d6402bf556fde5e53c817a54c1afe5"
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    "datePublished": "2026-09-16T10:33:01.545Z",
    "dateReserved": "2026-09-11T19:38:34.779Z",
    "dateUpdated": "2026-10-19T08:56:00.678Z",
    "state": "PUBLISHED"
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      "id": "msrc_CVE-2026-89986",
      "initial_release_date": "2026-10-20T22:22:02.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()",
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          }
        ],
        "id": "CVE-2026-89986",
        "lastModified": "2026-10-19T09:18:45.613",
        "metrics": {
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                "attackVector": "LOCAL",
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                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
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      "current_release_date": "2026-10-29T13:28:47+00:00",
      "cve": "CVE-2026-89986",
      "id": "CVE-2026-89986",
      "initial_release_date": "2026-09-16T00:00:00+00:00",
      "product_status:known_affected": "91",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()",
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      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "low",
      "current_release_date": "2026-10-20T00:52:26Z",
      "cve": "CVE-2026-89986",
      "id": "CVE-2026-89986",
      "initial_release_date": "2026-09-17T16:32:40Z",
      "product_status:known_affected": "30",
      "product_status:known_not_affected": "318",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89986",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-89986.json",
      "version": "5"
    }
  }
}



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