bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT

{
  "id": "bcf950787f82d887a2eb9a4314349f6f6aba8aaedd6d9279057bcea6bf64f042",
  "url": "https://osv.dev/vulnerability/CVE-2025-21825",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT During the update procedure, when overwrite element in a pre-allocated htab, the freeing of old_element is protected by the bucket lock. The reason why the bucket lock is necessary is that the old_element has already been stashed in htab->extra_elems after alloc_htab_elem() returns. If freeing the old_element after the bucket lock is unlocked, the stashed element may be reused by concurrent update procedure and the freeing of old_element will run concurrently with the reuse of the old_element. However, the invocation of check_and_free_fields() may acquire a spin-lock which violates the lockdep rule because its caller has already held a raw-spin-lock (bucket lock). The following warning will be reported when such race happens: BUG: scheduling while atomic: test_progs/676/0x00000003 3 locks held by test_progs/676: #0: ffffffff864b0240 (rcu_read_lock_trace){....}-{0:0}, at: bpf_prog_test_run_syscall+0x2c0/0x830 #1: ffff88810e961188 (&htab->lockdep_key){....}-{2:2}, at: htab_map_update_elem+0x306/0x1500 #2: ffff8881f4eac1b8 (&base->softirq_expiry_lock){....}-{2:2}, at: hrtimer_cancel_wait_running+0xe9/0x1b0 Modules linked in: bpf_testmod(O) Preemption disabled at: [] htab_map_update_elem+0x293/0x1500 CPU: 0 UID: 0 PID: 676 Comm: test_progs Tainted: G ... 6.12.0+ #11 Tainted: [W]=WARN, [O]=OOT_MODULE Hardware name: QEMU Standard PC (i440FX + PIIX, 19",
    "evidence": "osv:CVE-2025-21825",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.13",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.13.2",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-21825",
      "aliases": [
        "CVE-2025-21825"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "b00628b1c7d595ae5b544e059c27b1f5828314b4"
                },
                {
                  "fixed": "50e44aa5f9905d237c245b8012937ef4dd971dcb"
                },
                {
                  "fixed": "33e47d9573075342a41783a55c8c67bc71246fc1"
                },
                {
                  "fixed": "fbeda3d939ca10063aafa7a77cc0f409d82cda88"
                },
                {
                  "fixed": "58f038e6d209d2dd862fcf5de55407855856794d"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21825.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.15.0"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.13"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.13.2"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21825.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:35.961370270Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/33e47d9573075342a41783a55c8c67bc71246fc1",
        "https://git.kernel.org/stable/c/50e44aa5f9905d237c245b8012937ef4dd971dcb",
        "https://git.kernel.org/stable/c/58f038e6d209d2dd862fcf5de55407855856794d",
        "https://git.kernel.org/stable/c/fbeda3d939ca10063aafa7a77cc0f409d82cda88",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21825.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-21825",
        "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/2025/21xxx/CVE-2025-21825.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-21825",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 503467,
  "published_at": "2025-03-06T16:04:31.576+00:00"
}