CVE-2025-39901 (GCVE-0-2025-39901)
Vulnerability from cvelistv5
Published
2025-10-01 07:42
Modified
2025-10-01 07:42
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: i40e: remove read access to debugfs files The 'command' and 'netdev_ops' debugfs files are a legacy debugging interface supported by the i40e driver since its early days by commit 02e9c290814c ("i40e: debugfs interface"). Both of these debugfs files provide a read handler which is mostly useless, and which is implemented with questionable logic. They both use a static 256 byte buffer which is initialized to the empty string. In the case of the 'command' file this buffer is literally never used and simply wastes space. In the case of the 'netdev_ops' file, the last command written is saved here. On read, the files contents are presented as the name of the device followed by a colon and then the contents of their respective static buffer. For 'command' this will always be "<device>: ". For 'netdev_ops', this will be "<device>: <last command written>". But note the buffer is shared between all devices operated by this module. At best, it is mostly meaningless information, and at worse it could be accessed simultaneously as there doesn't appear to be any locking mechanism. We have also recently received multiple reports for both read functions about their use of snprintf and potential overflow that could result in reading arbitrary kernel memory. For the 'command' file, this is definitely impossible, since the static buffer is always zero and never written to. For the 'netdev_ops' file, it does appear to be possible, if the user carefully crafts the command input, it will be copied into the buffer, which could be large enough to cause snprintf to truncate, which then causes the copy_to_user to read beyond the length of the buffer allocated by kzalloc. A minimal fix would be to replace snprintf() with scnprintf() which would cap the return to the number of bytes written, preventing an overflow. A more involved fix would be to drop the mostly useless static buffers, saving 512 bytes and modifying the read functions to stop needing those as input. Instead, lets just completely drop the read access to these files. These are debug interfaces exposed as part of debugfs, and I don't believe that dropping read access will break any script, as the provided output is pretty useless. You can find the netdev name through other more standard interfaces, and the 'netdev_ops' interface can easily result in garbage if you issue simultaneous writes to multiple devices at once. In order to properly remove the i40e_dbg_netdev_ops_buf, we need to refactor its write function to avoid using the static buffer. Instead, use the same logic as the i40e_dbg_command_write, with an allocated buffer. Update the code to use this instead of the static buffer, and ensure we free the buffer on exit. This fixes simultaneous writes to 'netdev_ops' on multiple devices, and allows us to remove the now unused static buffer along with removing the read access.
References
Impacted products
Vendor Product Version
Linux Linux Version: 02e9c290814cc143ceccecb14eac3e7a05da745e
Version: 02e9c290814cc143ceccecb14eac3e7a05da745e
Version: 02e9c290814cc143ceccecb14eac3e7a05da745e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ethernet/intel/i40e/i40e_debugfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.12"
            },
            {
              "lessThan": "3.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.46",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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                  "versionEndExcluding": "6.12.46",
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                  "vulnerable": true
                },
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni40e: remove read access to debugfs files\n\nThe \u0027command\u0027 and \u0027netdev_ops\u0027 debugfs files are a legacy debugging\ninterface supported by the i40e driver since its early days by commit\n02e9c290814c (\"i40e: debugfs interface\").\n\nBoth of these debugfs files provide a read handler which is mostly useless,\nand which is implemented with questionable logic. They both use a static\n256 byte buffer which is initialized to the empty string. In the case of\nthe \u0027command\u0027 file this buffer is literally never used and simply wastes\nspace. In the case of the \u0027netdev_ops\u0027 file, the last command written is\nsaved here.\n\nOn read, the files contents are presented as the name of the device\nfollowed by a colon and then the contents of their respective static\nbuffer. For \u0027command\u0027 this will always be \"\u003cdevice\u003e: \". For \u0027netdev_ops\u0027,\nthis will be \"\u003cdevice\u003e: \u003clast command written\u003e\". But note the buffer is\nshared between all devices operated by this module. At best, it is mostly\nmeaningless information, and at worse it could be accessed simultaneously\nas there doesn\u0027t appear to be any locking mechanism.\n\nWe have also recently received multiple reports for both read functions\nabout their use of snprintf and potential overflow that could result in\nreading arbitrary kernel memory. For the \u0027command\u0027 file, this is definitely\nimpossible, since the static buffer is always zero and never written to.\nFor the \u0027netdev_ops\u0027 file, it does appear to be possible, if the user\ncarefully crafts the command input, it will be copied into the buffer,\nwhich could be large enough to cause snprintf to truncate, which then\ncauses the copy_to_user to read beyond the length of the buffer allocated\nby kzalloc.\n\nA minimal fix would be to replace snprintf() with scnprintf() which would\ncap the return to the number of bytes written, preventing an overflow. A\nmore involved fix would be to drop the mostly useless static buffers,\nsaving 512 bytes and modifying the read functions to stop needing those as\ninput.\n\nInstead, lets just completely drop the read access to these files. These\nare debug interfaces exposed as part of debugfs, and I don\u0027t believe that\ndropping read access will break any script, as the provided output is\npretty useless. You can find the netdev name through other more standard\ninterfaces, and the \u0027netdev_ops\u0027 interface can easily result in garbage if\nyou issue simultaneous writes to multiple devices at once.\n\nIn order to properly remove the i40e_dbg_netdev_ops_buf, we need to\nrefactor its write function to avoid using the static buffer. Instead, use\nthe same logic as the i40e_dbg_command_write, with an allocated buffer.\nUpdate the code to use this instead of the static buffer, and ensure we\nfree the buffer on exit. This fixes simultaneous writes to \u0027netdev_ops\u0027 on\nmultiple devices, and allows us to remove the now unused static buffer\nalong with removing the read access."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-10-01T07:42:48.606Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/70d3dad7d5ad077965d7a63eed1942b7ba49bfb4"
        },
        {
          "url": "https://git.kernel.org/stable/c/7d190963b80f4cd99d7008615600aa7cc993c6ba"
        },
        {
          "url": "https://git.kernel.org/stable/c/9fcdb1c3c4ba134434694c001dbff343f1ffa319"
        }
      ],
      "title": "i40e: remove read access to debugfs files",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39901",
    "datePublished": "2025-10-01T07:42:48.606Z",
    "dateReserved": "2025-04-16T07:20:57.146Z",
    "dateUpdated": "2025-10-01T07:42:48.606Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-39901\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-01T08:15:32.860\",\"lastModified\":\"2025-10-02T19:12:17.160\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ni40e: remove read access to debugfs files\\n\\nThe \u0027command\u0027 and \u0027netdev_ops\u0027 debugfs files are a legacy debugging\\ninterface supported by the i40e driver since its early days by commit\\n02e9c290814c (\\\"i40e: debugfs interface\\\").\\n\\nBoth of these debugfs files provide a read handler which is mostly useless,\\nand which is implemented with questionable logic. They both use a static\\n256 byte buffer which is initialized to the empty string. In the case of\\nthe \u0027command\u0027 file this buffer is literally never used and simply wastes\\nspace. In the case of the \u0027netdev_ops\u0027 file, the last command written is\\nsaved here.\\n\\nOn read, the files contents are presented as the name of the device\\nfollowed by a colon and then the contents of their respective static\\nbuffer. For \u0027command\u0027 this will always be \\\"\u003cdevice\u003e: \\\". For \u0027netdev_ops\u0027,\\nthis will be \\\"\u003cdevice\u003e: \u003clast command written\u003e\\\". But note the buffer is\\nshared between all devices operated by this module. At best, it is mostly\\nmeaningless information, and at worse it could be accessed simultaneously\\nas there doesn\u0027t appear to be any locking mechanism.\\n\\nWe have also recently received multiple reports for both read functions\\nabout their use of snprintf and potential overflow that could result in\\nreading arbitrary kernel memory. For the \u0027command\u0027 file, this is definitely\\nimpossible, since the static buffer is always zero and never written to.\\nFor the \u0027netdev_ops\u0027 file, it does appear to be possible, if the user\\ncarefully crafts the command input, it will be copied into the buffer,\\nwhich could be large enough to cause snprintf to truncate, which then\\ncauses the copy_to_user to read beyond the length of the buffer allocated\\nby kzalloc.\\n\\nA minimal fix would be to replace snprintf() with scnprintf() which would\\ncap the return to the number of bytes written, preventing an overflow. A\\nmore involved fix would be to drop the mostly useless static buffers,\\nsaving 512 bytes and modifying the read functions to stop needing those as\\ninput.\\n\\nInstead, lets just completely drop the read access to these files. These\\nare debug interfaces exposed as part of debugfs, and I don\u0027t believe that\\ndropping read access will break any script, as the provided output is\\npretty useless. You can find the netdev name through other more standard\\ninterfaces, and the \u0027netdev_ops\u0027 interface can easily result in garbage if\\nyou issue simultaneous writes to multiple devices at once.\\n\\nIn order to properly remove the i40e_dbg_netdev_ops_buf, we need to\\nrefactor its write function to avoid using the static buffer. Instead, use\\nthe same logic as the i40e_dbg_command_write, with an allocated buffer.\\nUpdate the code to use this instead of the static buffer, and ensure we\\nfree the buffer on exit. This fixes simultaneous writes to \u0027netdev_ops\u0027 on\\nmultiple devices, and allows us to remove the now unused static buffer\\nalong with removing the read access.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/70d3dad7d5ad077965d7a63eed1942b7ba49bfb4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7d190963b80f4cd99d7008615600aa7cc993c6ba\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9fcdb1c3c4ba134434694c001dbff343f1ffa319\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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