CVE-2026-89984 (GCVE-0-2026-89984)
Vulnerability from cvelistv5
Published
2026-09-16 10:33
Modified
2026-10-19 08:55
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: perf/x86/intel: Fix kernel address leakages in LBR stack Before Arch LBR gained CPL filtering support, a user-only branch stack could still contain kernel addresses. As a result, kernel branch records may be exposed to user space even when PERF_SAMPLE_BRANCH_USER is requested. For example, on Intel Tiger Lake, the following command can still report SYSRET/ERET entries with kernel-space from addresses: $ ./perf record -e cycles:p -o - --branch-filter any,save_type,u -- \ ./perf bench syscall basic --loop 1000 | \ ./perf script -i - --fields brstack|tr ' ' '\n'| \ grep -E '0x[89a-f][0-9a-f]{15}' Total time: 0.000 [sec] 0.219000 usecs/op 4,566,210 ops/sec [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.551 MB - ] 0xffffffff93c001c8/0x7f12a2b1d647/P/-/-/16959/SYSRET/- 0xffffffff93c001c8/0x7f12a2b1d5c2/P/-/-/17535/SYSRET/- 0xffffffff93c01928/0x7f12a2861000/P/-/-/6719/ERET/- 0xffffffff93c01928/0x7f12a297a000/P/-/-/8575/ERET/- The problem is that intel_pmu_lbr_filter() does not fully validate the privilege level of sampled entries. It filters some mismatches based on the branch type and the to address, but it does not reject entries whose from address violates the requested branch privilege filter. Fix this by extending software filtering to validate both from and to addresses against br_sel. Any LBR entry contains kernel address does not match the requested user filter is dropped. This prevents kernel addresses from appearing in user-only branch stacks.
References
Impacted products
Vendor Product Version
Linux Linux Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
Version: 47125db27e47e9d44c878bf8925aa057824bb0d5
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/events/intel/lbr.c"
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          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
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      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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              "negate": false,
              "operator": "OR"
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          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/x86/intel: Fix kernel address leakages in LBR stack\n\nBefore Arch LBR gained CPL filtering support, a user-only branch stack\ncould still contain kernel addresses. As a result, kernel branch records\nmay be exposed to user space even when PERF_SAMPLE_BRANCH_USER is\nrequested.\n\nFor example, on Intel Tiger Lake, the following command can still report\nSYSRET/ERET entries with kernel-space from addresses:\n\n$ ./perf record -e cycles:p -o - --branch-filter any,save_type,u -- \\\n \t./perf bench syscall basic --loop 1000 | \\\n\t./perf script -i - --fields brstack|tr \u0027 \u0027 \u0027\\n\u0027| \\\n\tgrep -E \u00270x[89a-f][0-9a-f]{15}\u0027\n\n    Total time: 0.000 [sec]\n\n      0.219000 usecs/op\n     4,566,210 ops/sec\n[ perf record: Woken up 1 times to write data ]\n[ perf record: Captured and wrote 0.551 MB - ]\n0xffffffff93c001c8/0x7f12a2b1d647/P/-/-/16959/SYSRET/-\n0xffffffff93c001c8/0x7f12a2b1d5c2/P/-/-/17535/SYSRET/-\n0xffffffff93c01928/0x7f12a2861000/P/-/-/6719/ERET/-\n0xffffffff93c01928/0x7f12a297a000/P/-/-/8575/ERET/-\n\nThe problem is that intel_pmu_lbr_filter() does not fully validate the\nprivilege level of sampled entries. It filters some mismatches based on\nthe branch type and the to address, but it does not reject entries whose\nfrom address violates the requested branch privilege filter.\n\nFix this by extending software filtering to validate both from and to\naddresses against br_sel. Any LBR entry contains kernel address does not\nmatch the requested user filter is dropped. This prevents kernel\naddresses from appearing in user-only branch stacks."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:55:58.750Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f3705db4e6378cc1b91a38ce0fe2f879055e23ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/b589147f54adc62e4172e4acf079ad5fb7b3687f"
        },
        {
          "url": "https://git.kernel.org/stable/c/be0628a101ac05b085aaa4f650d48bd3915e80fa"
        },
        {
          "url": "https://git.kernel.org/stable/c/ca19a175e89b7de604fab736436cbab74030b47a"
        },
        {
          "url": "https://git.kernel.org/stable/c/6ac26161db27f7fb9d9e89ae240dbe52795496cc"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c492c8eba02698ca893a9a13388d2adf6dfb839"
        },
        {
          "url": "https://git.kernel.org/stable/c/68c4b780b266a435261a1e029bede5ee3c2735cc"
        },
        {
          "url": "https://git.kernel.org/stable/c/e2b0575900ff72aa82748af96e7bd564ade5157a"
        }
      ],
      "title": "perf/x86/intel: Fix kernel address leakages in LBR stack",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89984",
    "datePublished": "2026-09-16T10:33:00.162Z",
    "dateReserved": "2026-09-11T19:38:34.779Z",
    "dateUpdated": "2026-10-19T08:55:58.750Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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