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GHSA-C23V-6RX9-2699

Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 12:30

Details

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix infinite loop in pcpu_freelist push with one possible CPU

__pcpu_freelist_push() can loop forever when only one CPU is possible and an NMI re-enters pcpu_freelist_push() while the interrupted context holds that CPU's freelist lock.

After the current-CPU fast path fails, the fallback loop walks cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or when an SMP kernel is limited to one possible CPU with nr_cpus=1 or possible_cpus=1, there are no other possible CPUs to examine. The loop therefore makes no lock acquisition attempt and can never make progress.

The following stack was observed on a UP system:

NMI context: pcpu_freelist_push free_htab_elem htab_map_delete_elem [perf-event BPF program] __perf_event_overflow perf_event_nmi_handler exc_nmi

Interrupted context: __pcpu_freelist_push pcpu_freelist_push free_htab_elem htab_map_delete_elem [raw_tp/sys_enter BPF program] __bpf_trace_sys_enter do_syscall_64

raw_res_spin_lock() detects the same-CPU recursive acquisition and returns -EDEADLK, but the subsequent fallback loop has no candidate head on a system with one possible CPU.

Restore the extra fallback head that existed before the rqspinlock conversion. Keep the current-CPU fast path, then try the other possible CPUs and finally the extra head. The additional head lets a push, which cannot fail without losing a preallocated element, make progress when the only per-CPU head is held by the interrupted context.

Also check the extra head from the pop path so that nodes placed there can be reused.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89991"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T11:17:10Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix infinite loop in pcpu_freelist push with one possible CPU\n\n__pcpu_freelist_push() can loop forever when only one CPU is possible\nand an NMI re-enters pcpu_freelist_push() while the interrupted context\nholds that CPU\u0027s freelist lock.\n\nAfter the current-CPU fast path fails, the fallback loop walks\ncpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or\nwhen an SMP kernel is limited to one possible CPU with nr_cpus=1 or\npossible_cpus=1, there are no other possible CPUs to examine. The loop\ntherefore makes no lock acquisition attempt and can never make progress.\n\nThe following stack was observed on a UP system:\n\n  NMI context:\n    pcpu_freelist_push\n    free_htab_elem\n    htab_map_delete_elem\n    [perf-event BPF program]\n    __perf_event_overflow\n    perf_event_nmi_handler\n    exc_nmi\n\n  Interrupted context:\n    __pcpu_freelist_push\n    pcpu_freelist_push\n    free_htab_elem\n    htab_map_delete_elem\n    [raw_tp/sys_enter BPF program]\n    __bpf_trace_sys_enter\n    do_syscall_64\n\nraw_res_spin_lock() detects the same-CPU recursive acquisition and\nreturns -EDEADLK, but the subsequent fallback loop has no candidate head\non a system with one possible CPU.\n\nRestore the extra fallback head that existed before the rqspinlock\nconversion. Keep the current-CPU fast path, then try the other possible\nCPUs and finally the extra head. The additional head lets a push, which\ncannot fail without losing a preallocated element, make progress when the\nonly per-CPU head is held by the interrupted context.\n\nAlso check the extra head from the pop path so that nodes placed there\ncan be reused.",
  "id": "GHSA-c23v-6rx9-2699",
  "modified": "2026-09-16T12:30:44Z",
  "published": "2026-09-16T12:30:44Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89991"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a24a146ae2cb5d9faeea96d10010fcb6579abe1f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a5b5e62baceff9e252c6535cf42a027d04f226cf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/efebf6496685c93150df5bb0794363ae70c5f58a"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-89991 (GCVE-0-2026-89991)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-09-16 10:33

Title

bpf: Fix infinite loop in pcpu_freelist push with one possible CPU

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix infinite loop in pcpu_freelist push with one possible CPU __pcpu_freelist_push() can loop forever when only one CPU is possible and an NMI re-enters pcpu_freelist_push() while the interrupted context holds that CPU's freelist lock. After the current-CPU fast path fails, the fallback loop walks cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or when an SMP kernel is limited to one possible CPU with nr_cpus=1 or possible_cpus=1, there are no other possible CPUs to examine. The loop therefore makes no lock acquisition attempt and can never make progress. The following stack was observed on a UP system: NMI context: pcpu_freelist_push free_htab_elem htab_map_delete_elem [perf-event BPF program] __perf_event_overflow perf_event_nmi_handler exc_nmi Interrupted context: __pcpu_freelist_push pcpu_freelist_push free_htab_elem htab_map_delete_elem [raw_tp/sys_enter BPF program] __bpf_trace_sys_enter do_syscall_64 raw_res_spin_lock() detects the same-CPU recursive acquisition and returns -EDEADLK, but the subsequent fallback loop has no candidate head on a system with one possible CPU. Restore the extra fallback head that existed before the rqspinlock conversion. Keep the current-CPU fast path, then try the other possible CPUs and finally the extra head. The additional head lets a push, which cannot fail without losing a preallocated element, make progress when the only per-CPU head is held by the interrupted context. Also check the extra head from the pop path so that nodes placed there can be reused.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/a24a146ae2cb5d9fa…
https://git.kernel.org/stable/c/a5b5e62baceff9e25…
https://git.kernel.org/stable/c/efebf6496685c9315…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < a24a146ae2cb5d9faeea96d10010fcb6579abe1f (git) Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < a5b5e62baceff9e252c6535cf42a027d04f226cf (git) Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < efebf6496685c93150df5bb0794363ae70c5f58a (git)
Linux	Linux	Affected: 6.15 Unaffected: 0 , < 6.15 (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.2.5 , ≤ 7.2.* (semver) Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)

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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
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          "programFiles": [
            "kernel/bpf/percpu_freelist.c",
            "kernel/bpf/percpu_freelist.h"
          ],
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          "versions": [
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              "versionType": "git"
            },
            {
              "lessThan": "a5b5e62baceff9e252c6535cf42a027d04f226cf",
              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "efebf6496685c93150df5bb0794363ae70c5f58a",
              "status": "affected",
              "version": "f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
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              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
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            }
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          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
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                },
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix infinite loop in pcpu_freelist push with one possible CPU\n\n__pcpu_freelist_push() can loop forever when only one CPU is possible\nand an NMI re-enters pcpu_freelist_push() while the interrupted context\nholds that CPU\u0027s freelist lock.\n\nAfter the current-CPU fast path fails, the fallback loop walks\ncpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or\nwhen an SMP kernel is limited to one possible CPU with nr_cpus=1 or\npossible_cpus=1, there are no other possible CPUs to examine. The loop\ntherefore makes no lock acquisition attempt and can never make progress.\n\nThe following stack was observed on a UP system:\n\n  NMI context:\n    pcpu_freelist_push\n    free_htab_elem\n    htab_map_delete_elem\n    [perf-event BPF program]\n    __perf_event_overflow\n    perf_event_nmi_handler\n    exc_nmi\n\n  Interrupted context:\n    __pcpu_freelist_push\n    pcpu_freelist_push\n    free_htab_elem\n    htab_map_delete_elem\n    [raw_tp/sys_enter BPF program]\n    __bpf_trace_sys_enter\n    do_syscall_64\n\nraw_res_spin_lock() detects the same-CPU recursive acquisition and\nreturns -EDEADLK, but the subsequent fallback loop has no candidate head\non a system with one possible CPU.\n\nRestore the extra fallback head that existed before the rqspinlock\nconversion. Keep the current-CPU fast path, then try the other possible\nCPUs and finally the extra head. The additional head lets a push, which\ncannot fail without losing a preallocated element, make progress when the\nonly per-CPU head is held by the interrupted context.\n\nAlso check the extra head from the pop path so that nodes placed there\ncan be reused."
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        },
        {
          "url": "https://git.kernel.org/stable/c/efebf6496685c93150df5bb0794363ae70c5f58a"
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    "datePublished": "2026-09-16T10:33:05.097Z",
    "dateReserved": "2026-09-11T19:38:34.780Z",
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    "state": "PUBLISHED"
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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