CVE-2026-89986 (GCVE-0-2026-89986)
Vulnerability from cvelistv5
Published
2026-09-16 10:33
Modified
2026-10-19 08:56
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/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.
References
Impacted products
Vendor Product Version
Linux Linux Version: fa3bea4e1f8202d787709b7e3654eb0a99aed758
Version: fa3bea4e1f8202d787709b7e3654eb0a99aed758
Version: fa3bea4e1f8202d787709b7e3654eb0a99aed758
Version: fa3bea4e1f8202d787709b7e3654eb0a99aed758
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/mempolicy.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "bcb3d0c867ee40dc48e9c085bf328fbc679b6656",
              "status": "affected",
              "version": "fa3bea4e1f8202d787709b7e3654eb0a99aed758",
              "versionType": "git"
            },
            {
              "lessThan": "0ceda28f371df9e0bbdaa29214f71fe8298f23d8",
              "status": "affected",
              "version": "fa3bea4e1f8202d787709b7e3654eb0a99aed758",
              "versionType": "git"
            },
            {
              "lessThan": "2943f1f4b7f2816177060eb9f551f2e6d8b629ba",
              "status": "affected",
              "version": "fa3bea4e1f8202d787709b7e3654eb0a99aed758",
              "versionType": "git"
            },
            {
              "lessThan": "540e583b66d6402bf556fde5e53c817a54c1afe5",
              "status": "affected",
              "version": "fa3bea4e1f8202d787709b7e3654eb0a99aed758",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "mm/mempolicy.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.110",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "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."
        }
      ],
      "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 - 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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:56:00.678Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bcb3d0c867ee40dc48e9c085bf328fbc679b6656"
        },
        {
          "url": "https://git.kernel.org/stable/c/0ceda28f371df9e0bbdaa29214f71fe8298f23d8"
        },
        {
          "url": "https://git.kernel.org/stable/c/2943f1f4b7f2816177060eb9f551f2e6d8b629ba"
        },
        {
          "url": "https://git.kernel.org/stable/c/540e583b66d6402bf556fde5e53c817a54c1afe5"
        }
      ],
      "title": "mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89986",
    "datePublished": "2026-09-16T10:33:01.545Z",
    "dateReserved": "2026-09-11T19:38:34.779Z",
    "dateUpdated": "2026-10-19T08:56:00.678Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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