github - ghsa-w922-jv62-78r5

GHSA-W922-JV62-78R5

Vulnerability from github – Published: 2025-07-25 15:30 – Updated: 2025-11-19 18:31

Details

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.

Severity ?

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38433"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-07-25T15:15:28Z",
    "severity": "MODERATE"
  },
  "details": "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`.",
  "id": "GHSA-w922-jv62-78r5",
  "modified": "2025-11-19T18:31:16Z",
  "published": "2025-07-25T15:30:54Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38433"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0a24b00dcde83934a3cc13e4c6b775522903496b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8d90d9872edae7e78c3a12b98e239bfaa66f3639"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-38433 (GCVE-0-2025-38433)

Vulnerability from cvelistv5 – Published: 2025-07-25 14:32 – Updated: 2025-07-28 04:22

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`.

Severity ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/0a24b00dcde83934a…
	https://git.kernel.org/stable/c/8d90d9872edae7e78…

Impacted products

Vendor

Product

Version

Linux

Affected: a44fb5722199de8338d991db5ad3d509192179bb , < 0a24b00dcde83934a3cc13e4c6b775522903496b (git)
Affected: a44fb5722199de8338d991db5ad3d509192179bb , < 8d90d9872edae7e78c3a12b98e239bfaa66f3639 (git)

Linux

Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.15.5 , ≤ 6.15.* (semver)
Unaffected: 6.16 , ≤ * (original_commit_for_fix)

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{
  "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"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-W922-JV62-78R5

CVE-2025-38433 (GCVE-0-2025-38433)

Tags

Sightings

Nomenclature