bpf: Fix NMI/tracepoint re-entry deadlock on lru locks

{
  "id": "c43aa289e68e77b330993d2be851bd97fbfab9ffef83f939a956be871b35af6c",
  "url": "https://osv.dev/vulnerability/CVE-2026-74337",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Fix NMI/tracepoint re-entry deadlock on lru locks",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NMI/tracepoint re-entry deadlock on lru locks NMI and tracepoint BPF programs can re-enter the per-CPU or global LRU lock that bpf_lru_pop_free()/push_free() already hold on the same CPU, AA-deadlocking. Lockdep reports \"inconsistent {INITIAL USE} -> {IN-NMI}\" on &l->lock (syzbot c69a0a2c816716f1e0d5) and \"possible recursive locking detected\" on &loc_l->lock (syzbot 18b26edb69b2e19f3b33). Prior trylock and rqspinlock based fixes (see links) were nacked because compromised on reliability. This patch converts every LRU lock site to rqspinlock_t and adds a recovery path for some failure windows to avoid node leaks. Failure recovery: - *_pop_free top-level: return NULL; prealloc_lru_pop() already treats that as no-free-element (-ENOMEM). - Cross-CPU steal: skip the victim's locked loc_l, try next CPU. - Post-steal local lock fail: publish stolen node to lockless per-CPU free_llist; next pop on this CPU picks it up. - push_free fail: mark node pending_free=1. __local_list_flush(), __local_list_pop_pending() reclaim the node from pending_list. __bpf_lru_list_shrink_inactive() reclaims the node from inactive list. Nodes from active list are reclaimed by __bpf_lru_list_shrink() or after __bpf_lru_list_rotate_active() demotes it to the inactive.",
    "evidence": "osv:CVE-2026-74337",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-74337",
      "aliases": [
        "CVE-2026-74337"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "3a08c2fd763450a927d1130de078d6f9e74944fb"
                },
                {
                  "fixed": "8b0510cc3a4a000d4ed1a56cd96231f3d3ba94c5"
                },
                {
                  "fixed": "440a2fdbb40608d55a7b11f2be53592a3785131d"
                },
                {
                  "fixed": "89edbdfc5d0308cef57b71359331de5c4ddbf763"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74337.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.10.0"
                },
                {
                  "fixed": "6.18.40"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.5"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74337.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.854616839Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/440a2fdbb40608d55a7b11f2be53592a3785131d",
        "https://git.kernel.org/stable/c/89edbdfc5d0308cef57b71359331de5c4ddbf763",
        "https://git.kernel.org/stable/c/8b0510cc3a4a000d4ed1a56cd96231f3d3ba94c5",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74337.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74337",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74337.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-74337",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518515,
  "published_at": "2026-08-15T05:58:28.518+00:00"
}