FKIE_CVE-2026-98038

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 11:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs bpf_refcount_acquire() is fallible for a borrowed reference because the object may have reached a zero refcount. The verifier therefore keeps KF_RET_NULL on the return value unless the argument is an owning reference. An RCU-protected load of a local kptr is marked MEM_ALLOC, but it only receives NON_OWN_REF when the pointee contains a graph node. A refcounted object without a graph node consequently looks like an owning reference even though the loaded register has no acquired reference state. If the program drops the last real reference while remaining in the RCU critical section, refcount_inc_not_zero() returns NULL while the verifier treats the result as non-NULL. Only classify the argument as owning when it is backed by a verifier-tracked reference. This retains the non-NULL return for pointers from bpf_obj_new(), bpf_kptr_xchg(), or an earlier successful acquisition, while requiring a NULL check for borrowed RCU kptrs. [ kkd: Rewrote commit log ]
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/85074498228a2500ea8b8039c49cc1ab8ad5328f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dc36739e5cc9f60485418a910b42bc95339218d2
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "85074498228a2500ea8b8039c49cc1ab8ad5328f",
              "status": "affected",
              "version": "1b12171533a9bb23cf6fba7262b479028b65e1e8",
              "versionType": "git"
            },
            {
              "lessThan": "dc36739e5cc9f60485418a910b42bc95339218d2",
              "status": "affected",
              "version": "1b12171533a9bb23cf6fba7262b479028b65e1e8",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Keep refcount_acquire nullable for borrowed RCU kptrs\n\nbpf_refcount_acquire() is fallible for a borrowed reference because the\nobject may have reached a zero refcount. The verifier therefore keeps\nKF_RET_NULL on the return value unless the argument is an owning reference.\n\nAn RCU-protected load of a local kptr is marked MEM_ALLOC, but it only\nreceives NON_OWN_REF when the pointee contains a graph node. A refcounted\nobject without a graph node consequently looks like an owning reference\neven though the loaded register has no acquired reference state. If the\nprogram drops the last real reference while remaining in the RCU critical\nsection, refcount_inc_not_zero() returns NULL while the verifier treats the\nresult as non-NULL.\n\nOnly classify the argument as owning when it is backed by a verifier-tracked\nreference. This retains the non-NULL return for pointers from bpf_obj_new(),\nbpf_kptr_xchg(), or an earlier successful acquisition, while requiring a\nNULL check for borrowed RCU kptrs.\n\n[ kkd: Rewrote commit log ]"
    }
  ],
  "id": "CVE-2026-98038",
  "lastModified": "2026-09-25T11:17:32.560",
  "metrics": {},
  "published": "2026-09-25T11:17:32.560",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/85074498228a2500ea8b8039c49cc1ab8ad5328f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dc36739e5cc9f60485418a910b42bc95339218d2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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