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

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-10-19 08:56
VLAI
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 CNA under the mitre root
CNA scorecard D 53/100 over 6847 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < a24a146ae2cb5d9faeea96d10010fcb6579abe1f (git)
Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < a5b5e62baceff9e252c6535cf42a027d04f226cf (git)
Affected: f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb , < efebf6496685c93150df5bb0794363ae70c5f58a (git)
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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 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
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          "product": "Linux",
          "programFiles": [
            "kernel/bpf/percpu_freelist.c",
            "kernel/bpf/percpu_freelist.h"
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          "vendor": "Linux",
          "versions": [
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          "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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        "dateUpdated": "2026-10-19T08:56:05.536Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89991",
    "datePublished": "2026-09-16T10:33:05.097Z",
    "dateReserved": "2026-09-11T19:38:34.780Z",
    "dateUpdated": "2026-10-19T08:56:05.536Z",
    "state": "PUBLISHED"
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      "id": "msrc_CVE-2026-89991",
      "initial_release_date": "2026-10-20T22:22:10.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
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      "title": "bpf: Fix infinite loop in pcpu_freelist push with one possible CPU",
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            "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."
          }
        ],
        "id": "CVE-2026-89991",
        "lastModified": "2026-10-19T09:18:46.253",
        "metrics": {},
        "published": "2026-09-16T11:17:10.240",
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      "cve": "CVE-2026-89991",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Fix infinite loop in pcpu_freelist push with one possible CPU",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89991.json",
      "version": "3"
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      "cve": "CVE-2026-89991",
      "id": "CVE-2026-89991",
      "initial_release_date": "2026-09-17T16:32:29Z",
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      "status": "interim",
      "title": "SUSE CVE CVE-2026-89991",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-89991.json",
      "version": "6"
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}



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