CVE-2025-38433 (GCVE-0-2025-38433)
Vulnerability from cvelistv5
Published
2025-07-25 14:32
Modified
2025-07-28 04:22
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: riscv: fix runtime constant support for nommu kernels the `__runtime_fixup_32` function does not handle the case where `val` is zero correctly (as might occur when patching a nommu kernel and referring to a physical address below the 4GiB boundary whose upper 32 bits are all zero) because nothing in the existing logic prevents the code from taking the `else` branch of both nop-checks and emitting two `nop` instructions. This leaves random garbage in the register that is supposed to receive the upper 32 bits of the pointer instead of zero that when combined with the value for the lower 32 bits yields an invalid pointer and causes a kernel panic when that pointer is eventually accessed. The author clearly considered the fact that if the `lui` is converted into a `nop` that the second instruction needs to be adjusted to become an `li` instead of an `addi`, hence introducing the `addi_insn_mask` variable, but didn't follow that logic through fully to the case where the `else` branch executes. To fix it just adjust the logic to ensure that the second `else` branch is not taken if the first instruction will be patched to a `nop`.
References
Impacted products
Vendor Product Version
Linux Linux Version: a44fb5722199de8338d991db5ad3d509192179bb
Version: a44fb5722199de8338d991db5ad3d509192179bb
 Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/riscv/include/asm/runtime-const.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0a24b00dcde83934a3cc13e4c6b775522903496b",
              "status": "affected",
              "version": "a44fb5722199de8338d991db5ad3d509192179bb",
              "versionType": "git"
            },
            {
              "lessThan": "8d90d9872edae7e78c3a12b98e239bfaa66f3639",
              "status": "affected",
              "version": "a44fb5722199de8338d991db5ad3d509192179bb",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/riscv/include/asm/runtime-const.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.15.*",
              "status": "unaffected",
              "version": "6.15.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.16",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.15.5",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.16",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: fix runtime constant support for nommu kernels\n\nthe `__runtime_fixup_32` function does not handle the case where `val` is\nzero correctly (as might occur when patching a nommu kernel and referring\nto a physical address below the 4GiB boundary whose upper 32 bits are all\nzero) because nothing in the existing logic prevents the code from taking\nthe `else` branch of both nop-checks and emitting two `nop` instructions.\n\nThis leaves random garbage in the register that is supposed to receive the\nupper 32 bits of the pointer instead of zero that when combined with the\nvalue for the lower 32 bits yields an invalid pointer and causes a kernel\npanic when that pointer is eventually accessed.\n\nThe author clearly considered the fact that if the `lui` is converted into\na `nop` that the second instruction needs to be adjusted to become an `li`\ninstead of an `addi`, hence introducing the `addi_insn_mask` variable, but\ndidn\u0027t follow that logic through fully to the case where the `else` branch\nexecutes. To fix it just adjust the logic to ensure that the second `else`\nbranch is not taken if the first instruction will be patched to a `nop`."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-07-28T04:22:06.009Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0a24b00dcde83934a3cc13e4c6b775522903496b"
        },
        {
          "url": "https://git.kernel.org/stable/c/8d90d9872edae7e78c3a12b98e239bfaa66f3639"
        }
      ],
      "title": "riscv: fix runtime constant support for nommu kernels",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38433",
    "datePublished": "2025-07-25T14:32:07.122Z",
    "dateReserved": "2025-04-16T04:51:24.015Z",
    "dateUpdated": "2025-07-28T04:22:06.009Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-38433\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-07-25T15:15:28.570\",\"lastModified\":\"2025-07-25T15:29:19.837\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nriscv: fix runtime constant support for nommu kernels\\n\\nthe `__runtime_fixup_32` function does not handle the case where `val` is\\nzero correctly (as might occur when patching a nommu kernel and referring\\nto a physical address below the 4GiB boundary whose upper 32 bits are all\\nzero) because nothing in the existing logic prevents the code from taking\\nthe `else` branch of both nop-checks and emitting two `nop` instructions.\\n\\nThis leaves random garbage in the register that is supposed to receive the\\nupper 32 bits of the pointer instead of zero that when combined with the\\nvalue for the lower 32 bits yields an invalid pointer and causes a kernel\\npanic when that pointer is eventually accessed.\\n\\nThe author clearly considered the fact that if the `lui` is converted into\\na `nop` that the second instruction needs to be adjusted to become an `li`\\ninstead of an `addi`, hence introducing the `addi_insn_mask` variable, but\\ndidn\u0027t follow that logic through fully to the case where the `else` branch\\nexecutes. To fix it just adjust the logic to ensure that the second `else`\\nbranch is not taken if the first instruction will be patched to a `nop`.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0a24b00dcde83934a3cc13e4c6b775522903496b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8d90d9872edae7e78c3a12b98e239bfaa66f3639\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.