CVE-2026-97921 (GCVE-0-2026-97921)
Vulnerability from cvelistv5
Published
2026-09-25 10:22
Modified
2026-10-19 09:10
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Free histogram the field rejected for a bad modifier Writing a hist trigger whose value or variable carries a modifier that is not allowed there leaks the fields that were built for it. __create_val_field() takes the field from parse_expr() and stores it in hist_data->fields[] only after the modifier checks have run: hist_field = parse_expr(hist_data, file, field_str, flags, var_name, &n_subexprs); ... if (hist_field->flags & HIST_FIELD_FL_VAR) { if (hist_field->flags & (...)) goto err; } else { if (hist_field->flags & (...)) goto err; } hist_data->fields[val_idx] = hist_field; Both checks jump past that store, and the err label returns without freeing anything. The error unwinds to create_hist_data(), which calls destroy_hist_data() -> destroy_hist_fields(), and that reaches a field only by walking fields[]. A field that never got there is unreachable. commit e0213434fe3e ("tracing: Do not let histogram values have some modifiers") set ret to -EINVAL and fell through to the store, which left the field owned by fields[] and freed along with the rest of hist_data. Splitting the check into a value case and a variable case replaced that fall-through with a goto that skips it. With CONFIG_DEBUG_KMEMLEAK, 200 writes of # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \ events/sched/sched_switch/trigger each correctly rejected with -EINVAL, leave 332 unreferenced objects (63744 bytes) reported at create_hist_field(); 200 install and remove cycles of a valid trigger leave none. A '.log2' field is two allocations, since create_hist_field() puts the plain field in operands[0] of the log2 field, and both are reported. Use destroy_hist_field() rather than __destroy_hist_field() so that operands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF, which is what an operand owned by hist_data->var_refs[] needs; the rejected field itself is never a var ref, because a var ref never carries a modifier flag.
References
Impacted products
Vendor Product Version
Linux Linux Version: 7403630eb94c1d664fb873f967427ef2f6ee3699
Version: e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c
Version: e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c
Version: e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c
Version: e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c
Version: e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c
Version: 8d505d06d7330f5d67d3e5e9e1c647fb0b10ddad
Version: 6.1.33   ≤
Version: 6.3.7   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_events_hist.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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            {
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              "versionType": "git"
            },
            {
              "lessThan": "6.1.189",
              "status": "affected",
              "version": "6.1.33",
              "versionType": "semver"
            },
            {
              "lessThan": "6.4",
              "status": "affected",
              "version": "6.3.7",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_events_hist.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.189",
                  "versionStartIncluding": "6.1.33",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.158",
                  "versionStartIncluding": "6.4",
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                },
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.7",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
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                  "vulnerable": true
                },
                {
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                  "versionStartIncluding": "6.3.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fields that were built for it.\n\n__create_val_field() takes the field from parse_expr() and stores it in\nhist_data-\u003efields[] only after the modifier checks have run:\n\n\thist_field = parse_expr(hist_data, file, field_str, flags, var_name,\n\t\t\t\t\u0026n_subexprs);\n\t...\n\tif (hist_field-\u003eflags \u0026 HIST_FIELD_FL_VAR) {\n\t\tif (hist_field-\u003eflags \u0026 (...))\n\t\t\tgoto err;\n\t} else {\n\t\tif (hist_field-\u003eflags \u0026 (...))\n\t\t\tgoto err;\n\t}\n\n\thist_data-\u003efields[val_idx] = hist_field;\n\nBoth checks jump past that store, and the err label returns without\nfreeing anything. The error unwinds to create_hist_data(), which calls\ndestroy_hist_data() -\u003e destroy_hist_fields(), and that reaches a field\nonly by walking fields[]. A field that never got there is unreachable.\n\ncommit e0213434fe3e (\"tracing: Do not let histogram values have some\nmodifiers\") set ret to -EINVAL and fell through to the store, which left\nthe field owned by fields[] and freed along with the rest of hist_data.\nSplitting the check into a value case and a variable case replaced that\nfall-through with a goto that skips it.\n\nWith CONFIG_DEBUG_KMEMLEAK, 200 writes of\n\n  # echo \u0027hist:keys=prev_pid:vals=next_pid.log2\u0027 \u003e \\\n\t events/sched/sched_switch/trigger\n\neach correctly rejected with -EINVAL, leave 332 unreferenced objects\n(63744 bytes) reported at create_hist_field(); 200 install and remove\ncycles of a valid trigger leave none. A \u0027.log2\u0027 field is two\nallocations, since create_hist_field() puts the plain field in\noperands[0] of the log2 field, and both are reported.\n\nUse destroy_hist_field() rather than __destroy_hist_field() so that\noperands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF,\nwhich is what an operand owned by hist_data-\u003evar_refs[] needs; the\nrejected field itself is never a var ref, because a var ref never carries\na modifier flag."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:10:48.148Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a2652fcf96b63e9da04951e4e58e6a0672df695d"
        },
        {
          "url": "https://git.kernel.org/stable/c/3d42fed18b2c5707b6332ebe87b789fd768eb01b"
        },
        {
          "url": "https://git.kernel.org/stable/c/e787361bb6b0026ea3eb4d3fa7a304c7fcb99555"
        },
        {
          "url": "https://git.kernel.org/stable/c/b22dc0add7d72b8bd9cae3188db0dd65da1c8652"
        },
        {
          "url": "https://git.kernel.org/stable/c/891c21f6d5673b2a519b536243bfc6dd2d35beb6"
        },
        {
          "url": "https://git.kernel.org/stable/c/230234d12ce42ab04132a32c3a848f07a5d27a71"
        }
      ],
      "title": "tracing: Free histogram the field rejected for a bad modifier",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97921",
    "datePublished": "2026-09-25T10:22:41.081Z",
    "dateReserved": "2026-09-25T10:18:58.202Z",
    "dateUpdated": "2026-10-19T09:10:48.148Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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