CVE-2026-98813 (GCVE-0-2026-98813)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:48 – Updated: 2026-10-19 09:26
VLAI
Title
bpf: Hold map BTF for the memory allocator destructor record
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Hold map BTF for the memory allocator destructor record bpf_ma_set_dtor() duplicates map->record so that the bpf_mem_alloc destructor can release the special fields of hash and rhash map elements once the allocator frees them for good. btf_record_dup() only acquires references on kernel and module BTF. Fields whose types live in the map BTF keep pointing into it: a kptr to a local type refers to map->btf, and a list_head or rb_root field carries a value_rec owned by the struct meta table of map->btf. That borrowed state can outlive the map. When RCU callbacks are still in flight, bpf_mem_alloc_destroy() copies the allocator and defers the final drain, together with the destructor context, to a workqueue. bpf_map_free() then frees map->record and drops the map's BTF reference as soon as map_free() returns. Once the program that loaded the BTF is gone as well, the BTF is freed while the worker still uses the duplicate. The worker dereferences it through btf_is_kernel() and btf_find_struct_meta() in bpf_obj_free_fields() when destroying elements that were freed under RCU, and through btf_is_kernel() in btf_record_free() when releasing the context itself: BUG: KASAN: slab-use-after-free in btf_is_kernel+0x19/0x30 Read of size 1 at addr ffff88811505dce8 by task kworker/u16:2/50 Workqueue: events_unbound free_mem_alloc_deferred Call Trace: btf_is_kernel+0x19/0x30 btf_record_free+0xc7/0xf0 htab_dtor_ctx_free+0x1a/0x30 free_mem_alloc_no_barrier+0x39/0x230 free_mem_alloc_deferred+0x2a/0x40 process_scheduled_works+0x5ce/0x9d0 worker_thread+0x42a/0x5e0 kthread+0x1f5/0x230 ret_from_fork+0x1dd/0x390 ret_from_fork_asm+0x1a/0x30 Allocated by task 358: __kmalloc_cache_noprof+0x287/0x510 btf_new_fd+0xf7/0x3d0 __sys_bpf+0x487/0x840 Freed by task 0: kfree+0x186/0x560 rcu_core+0x6f6/0xd40 Freeing a map that still holds more elements than the allocator's high watermark is enough to get there, because the bulk free during teardown queues the RCU callback that makes bpf_mem_alloc_destroy() defer. Non-preallocated hash maps and resizable hash maps both register the destructor and are affected alike. Keep one reference on the map BTF in the destructor context. Every non-kernel pointer in the duplicated record is either map->btf or memory owned by it, so a single reference covers kptrs, list heads, and rb roots, and mirrors what bpf_map_meta_alloc() does for the duplicated record of an inner map. Release it only after the duplicated record has been freed: the worker is preemptible and not in an RCU read-side critical section, so dropping the last reference first would let the BTF be freed while btf_record_free() still reads its fields.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6848 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1df97a7453eec80c1912c2d0360290a3970a7671 , < b506f5699e145196ee29d76cf1ca1cbb2202c055 (git)
Affected: 1df97a7453eec80c1912c2d0360290a3970a7671 , < ab39974240a0cff765f3bb9cce81d8001ffdb144 (git)
Affected: 451a84a3ad3c897c03181af433e7c98640730f1f (git)
Affected: 51a17f0ce19c4ee2a25cf16c93490d509b1ebb0a (git)
Affected: 6.12.112 , < 6.13 (semver)
Affected: 6.18.55 , < 6.19 (semver)
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Linux Linux Affected: 7.0
Unaffected: 0 , < 7.0 (semver)
Unaffected: 7.2.10 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/hashtab.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "7.0"
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              "status": "unaffected",
              "version": "0",
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              "version": "7.2.10",
              "versionType": "semver"
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              "version": "7.3",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Hold map BTF for the memory allocator destructor record\n\nbpf_ma_set_dtor() duplicates map-\u003erecord so that the bpf_mem_alloc\ndestructor can release the special fields of hash and rhash map elements\nonce the allocator frees them for good. btf_record_dup() only acquires\nreferences on kernel and module BTF. Fields whose types live in the map\nBTF keep pointing into it: a kptr to a local type refers to map-\u003ebtf,\nand a list_head or rb_root field carries a value_rec owned by the struct\nmeta table of map-\u003ebtf.\n\nThat borrowed state can outlive the map. When RCU callbacks are still in\nflight, bpf_mem_alloc_destroy() copies the allocator and defers the final\ndrain, together with the destructor context, to a workqueue.\nbpf_map_free() then frees map-\u003erecord and drops the map\u0027s BTF reference\nas soon as map_free() returns. Once the program that loaded the BTF is\ngone as well, the BTF is freed while the worker still uses the\nduplicate. The worker dereferences it through btf_is_kernel() and\nbtf_find_struct_meta() in bpf_obj_free_fields() when destroying elements\nthat were freed under RCU, and through btf_is_kernel() in\nbtf_record_free() when releasing the context itself:\n\n  BUG: KASAN: slab-use-after-free in btf_is_kernel+0x19/0x30\n  Read of size 1 at addr ffff88811505dce8 by task kworker/u16:2/50\n  Workqueue: events_unbound free_mem_alloc_deferred\n  Call Trace:\n   btf_is_kernel+0x19/0x30\n   btf_record_free+0xc7/0xf0\n   htab_dtor_ctx_free+0x1a/0x30\n   free_mem_alloc_no_barrier+0x39/0x230\n   free_mem_alloc_deferred+0x2a/0x40\n   process_scheduled_works+0x5ce/0x9d0\n   worker_thread+0x42a/0x5e0\n   kthread+0x1f5/0x230\n   ret_from_fork+0x1dd/0x390\n   ret_from_fork_asm+0x1a/0x30\n\n  Allocated by task 358:\n   __kmalloc_cache_noprof+0x287/0x510\n   btf_new_fd+0xf7/0x3d0\n   __sys_bpf+0x487/0x840\n\n  Freed by task 0:\n   kfree+0x186/0x560\n   rcu_core+0x6f6/0xd40\n\nFreeing a map that still holds more elements than the allocator\u0027s high\nwatermark is enough to get there, because the bulk free during teardown\nqueues the RCU callback that makes bpf_mem_alloc_destroy() defer.\nNon-preallocated hash maps and resizable hash maps both register the\ndestructor and are affected alike.\n\nKeep one reference on the map BTF in the destructor context. Every\nnon-kernel pointer in the duplicated record is either map-\u003ebtf or memory\nowned by it, so a single reference covers kptrs, list heads, and rb\nroots, and mirrors what bpf_map_meta_alloc() does for the duplicated\nrecord of an inner map. Release it only after the duplicated record has\nbeen freed: the worker is preemptible and not in an RCU read-side\ncritical section, so dropping the last reference first would let the\nBTF be freed while btf_record_free() still reads its fields."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:26:06.490Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/b506f5699e145196ee29d76cf1ca1cbb2202c055"
        },
        {
          "url": "https://git.kernel.org/stable/c/ab39974240a0cff765f3bb9cce81d8001ffdb144"
        }
      ],
      "title": "bpf: Hold map BTF for the memory allocator destructor record",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98813",
    "datePublished": "2026-10-18T15:48:59.745Z",
    "dateReserved": "2026-09-25T10:25:14.371Z",
    "dateUpdated": "2026-10-19T09:26:06.490Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "cve": "CVE-2026-98813",
      "date": "2026-11-03",
      "epss": "0.00155",
      "percentile": "0.04685"
    },
    "nvd": {
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                "product": "Linux",
                "programFiles": [
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                ],
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                "vendor": "Linux",
                "versions": [
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                    "version": "0",
                    "versionType": "semver"
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                    "version": "7.2.10",
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                  }
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              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Hold map BTF for the memory allocator destructor record\n\nbpf_ma_set_dtor() duplicates map-\u003erecord so that the bpf_mem_alloc\ndestructor can release the special fields of hash and rhash map elements\nonce the allocator frees them for good. btf_record_dup() only acquires\nreferences on kernel and module BTF. Fields whose types live in the map\nBTF keep pointing into it: a kptr to a local type refers to map-\u003ebtf,\nand a list_head or rb_root field carries a value_rec owned by the struct\nmeta table of map-\u003ebtf.\n\nThat borrowed state can outlive the map. When RCU callbacks are still in\nflight, bpf_mem_alloc_destroy() copies the allocator and defers the final\ndrain, together with the destructor context, to a workqueue.\nbpf_map_free() then frees map-\u003erecord and drops the map\u0027s BTF reference\nas soon as map_free() returns. Once the program that loaded the BTF is\ngone as well, the BTF is freed while the worker still uses the\nduplicate. The worker dereferences it through btf_is_kernel() and\nbtf_find_struct_meta() in bpf_obj_free_fields() when destroying elements\nthat were freed under RCU, and through btf_is_kernel() in\nbtf_record_free() when releasing the context itself:\n\n  BUG: KASAN: slab-use-after-free in btf_is_kernel+0x19/0x30\n  Read of size 1 at addr ffff88811505dce8 by task kworker/u16:2/50\n  Workqueue: events_unbound free_mem_alloc_deferred\n  Call Trace:\n   btf_is_kernel+0x19/0x30\n   btf_record_free+0xc7/0xf0\n   htab_dtor_ctx_free+0x1a/0x30\n   free_mem_alloc_no_barrier+0x39/0x230\n   free_mem_alloc_deferred+0x2a/0x40\n   process_scheduled_works+0x5ce/0x9d0\n   worker_thread+0x42a/0x5e0\n   kthread+0x1f5/0x230\n   ret_from_fork+0x1dd/0x390\n   ret_from_fork_asm+0x1a/0x30\n\n  Allocated by task 358:\n   __kmalloc_cache_noprof+0x287/0x510\n   btf_new_fd+0xf7/0x3d0\n   __sys_bpf+0x487/0x840\n\n  Freed by task 0:\n   kfree+0x186/0x560\n   rcu_core+0x6f6/0xd40\n\nFreeing a map that still holds more elements than the allocator\u0027s high\nwatermark is enough to get there, because the bulk free during teardown\nqueues the RCU callback that makes bpf_mem_alloc_destroy() defer.\nNon-preallocated hash maps and resizable hash maps both register the\ndestructor and are affected alike.\n\nKeep one reference on the map BTF in the destructor context. Every\nnon-kernel pointer in the duplicated record is either map-\u003ebtf or memory\nowned by it, so a single reference covers kptrs, list heads, and rb\nroots, and mirrors what bpf_map_meta_alloc() does for the duplicated\nrecord of an inner map. Release it only after the duplicated record has\nbeen freed: the worker is preemptible and not in an RCU read-side\ncritical section, so dropping the last reference first would let the\nBTF be freed while btf_record_free() still reads its fields."
          }
        ],
        "id": "CVE-2026-98813",
        "lastModified": "2026-10-19T10:19:45.330",
        "metrics": {},
        "published": "2026-10-18T16:17:35.427",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ab39974240a0cff765f3bb9cce81d8001ffdb144"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/b506f5699e145196ee29d76cf1ca1cbb2202c055"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-23T19:20:39+00:00",
      "cve": "CVE-2026-98813",
      "id": "CVE-2026-98813",
      "initial_release_date": "2026-10-18T00:00:00+00:00",
      "product_status:known_not_affected": "278",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Hold map BTF for the memory allocator destructor record",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98813.json",
      "version": "3"
    }
  }
}



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