{"cve":"CVE-2026-89991","nvd":{"published":"2026-09-16T11:17:10.240","modified":"2026-10-19T09:18:46.253","status":"Received","description":"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's 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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/a24a146ae2cb5d9faeea96d10010fcb6579abe1f","https://git.kernel.org/stable/c/a5b5e62baceff9e252c6535cf42a027d04f226cf","https://git.kernel.org/stable/c/efebf6496685c93150df5bb0794363ae70c5f58a"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:54:41.405518556+00:00"},"epss":{"cve":"CVE-2026-89991","score":0.00206,"percentile":0.10588,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}