virtio_net: Do not send RSS key if it is not supported

{
  "id": "1b9911b2ff0a446de389a906fbcfd061ce03d6aadcf7ffa6ffdc02fe899eee5a",
  "url": "https://osv.dev/vulnerability/CVE-2024-35981",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "virtio_net: Do not send RSS key if it is not supported",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: virtio_net: Do not send RSS key if it is not supported There is a bug when setting the RSS options in virtio_net that can break the whole machine, getting the kernel into an infinite loop. Running the following command in any QEMU virtual machine with virtionet will reproduce this problem: # ethtool -X eth0 hfunc toeplitz This is how the problem happens: 1) ethtool_set_rxfh() calls virtnet_set_rxfh() 2) virtnet_set_rxfh() calls virtnet_commit_rss_command() 3) virtnet_commit_rss_command() populates 4 entries for the rss scatter-gather 4) Since the command above does not have a key, then the last scatter-gatter entry will be zeroed, since rss_key_size == 0. sg_buf_size = vi->rss_key_size; 5) This buffer is passed to qemu, but qemu is not happy with a buffer with zero length, and do the following in virtqueue_map_desc() (QEMU function): if (!sz) { virtio_error(vdev, \"virtio: zero sized buffers are not allowed\"); 6) virtio_error() (also QEMU function) set the device as broken vdev->broken = true; 7) Qemu bails out, and do not repond this crazy kernel. 8) The kernel is waiting for the response to come back (function virtnet_send_command()) 9) The kernel is waiting doing the following : while (!virtqueue_get_buf(vi->cvq, &tmp) && !virtqueue_is_broken(vi->cvq)) cpu_relax(); 10) None of the following functions above is true, thus, the kernel loops here forever. Keeping in mind that virtqueue_is_broken() does not look",
    "evidence": "osv:CVE-2024-35981",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.90",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.29",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.8.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2024-35981",
      "aliases": [
        "CVE-2024-35981"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c7114b1249fa3b5f3a434606ba4cc89c4a27d618"
                },
                {
                  "fixed": "539a2b995a4ed93125cb0efae0f793b00ab2158b"
                },
                {
                  "fixed": "43a71c1b4b3a6d4db857b1435d271540279fc7de"
                },
                {
                  "fixed": "28e9a64638cd16bc1ecac9ff74ffeacb9fb652de"
                },
                {
                  "fixed": "059a49aa2e25c58f90b50151f109dd3c4cdb3a47"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-35981.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.18.0"
                },
                {
                  "fixed": "6.1.90"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.29"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.8.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-35981.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:46.059041317Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/059a49aa2e25c58f90b50151f109dd3c4cdb3a47",
        "https://git.kernel.org/stable/c/28e9a64638cd16bc1ecac9ff74ffeacb9fb652de",
        "https://git.kernel.org/stable/c/43a71c1b4b3a6d4db857b1435d271540279fc7de",
        "https://git.kernel.org/stable/c/539a2b995a4ed93125cb0efae0f793b00ab2158b",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/35xxx/CVE-2024-35981.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-35981",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/35xxx/CVE-2024-35981.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-35981",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 514044,
  "published_at": "2024-05-20T09:42:05.722+00:00"
}