svcrdma: Fix pcl_for_each_segment for empty chunks

{
  "id": "fa8ef15384d64addc1ceabd5ab0be43ab3aeb03ae8bfa128d852c2debc64ea88",
  "url": "https://osv.dev/vulnerability/CVE-2026-89532",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "svcrdma: Fix pcl_for_each_segment for empty chunks",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: svcrdma: Fix pcl_for_each_segment for empty chunks When a parsed chunk list contains a chunk whose ch_segcount is zero, pcl_for_each_segment computes its inclusive upper bound as &chunk->ch_segments[ch_segcount - 1]. ch_segcount is u32, so the subtraction wraps to 0xFFFFFFFF and the bound lands far past the ch_segments flex array. The loop body then walks unrelated memory at sizeof(struct svc_rdma_segment) stride until it faults. A zero-segcount chunk is reachable from the wire: xdr_check_write_chunk() only rejects segcount values greater than rc_maxpages, and pcl_alloc_write() links a freshly allocated chunk onto rc_write_pcl/rc_reply_pcl before its segment-fill loop runs, so a Write or Reply chunk advertising zero segments leaves ch_segcount == 0 on the list. When the transport has negotiated Send-With-Invalidate, svc_rdma_get_inv_rkey() iterates all four PCLs with pcl_for_each_segment and dereferences segment->rs_handle on each iteration, turning the underflow into an out-of-bounds read and a general protection fault. xdr_check_write_list / xdr_check_reply_chunk pcl_alloc_write() chunk = pcl_alloc_chunk(...) /* ch_segcount = 0 */ list_add_tail(&chunk->ch_list, &pcl->cl_chunks) /* fill loop iterates zero times for wire segcount 0 */ svc_rdma_get_inv_rkey() pcl_for_each_chunk(rc_write_pcl) pcl_for_each_segment(segment, chunk) pos <= &ch_segments[0u - 1u] /* 0xFFFFFFFF */ segment->rs_handle /* OOB read -> GPF",
    "evidence": "osv:CVE-2026-89532",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.15.221",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.188",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.109",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-89532",
      "aliases": [
        "CVE-2026-89532"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "78147ca8b4a9b6cf0e597ddd6bf17959e08376c2"
                },
                {
                  "fixed": "1e2e3481e39103a386b86be1c33eaef97cbdf16e"
                },
                {
                  "fixed": "3a78b841879c2a3243f74edc514236fb2907167f"
                },
                {
                  "fixed": "06d0390c37fa6714624af771bd72bbf1a7ed9bb1"
                },
                {
                  "fixed": "9c5a03c3dc505c0295339b0a1b9e4fe36447e482"
                },
                {
                  "fixed": "a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8"
                },
                {
                  "fixed": "6d33a7e6bf6c6b293a266a617201285a1ad32c56"
                },
                {
                  "fixed": "b7713a784c59515d0aba558c8f5df6a0164dd3a9"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89532.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.221"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.188"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.157"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.109"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.50"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89532.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.479570596Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/06d0390c37fa6714624af771bd72bbf1a7ed9bb1",
        "https://git.kernel.org/stable/c/1e2e3481e39103a386b86be1c33eaef97cbdf16e",
        "https://git.kernel.org/stable/c/3a78b841879c2a3243f74edc514236fb2907167f",
        "https://git.kernel.org/stable/c/6d33a7e6bf6c6b293a266a617201285a1ad32c56",
        "https://git.kernel.org/stable/c/9c5a03c3dc505c0295339b0a1b9e4fe36447e482",
        "https://git.kernel.org/stable/c/a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8",
        "https://git.kernel.org/stable/c/b7713a784c59515d0aba558c8f5df6a0164dd3a9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89532.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89532",
        "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/2026/89xxx/CVE-2026-89532.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89532",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 505902,
  "published_at": "2026-09-11T19:44:11.495+00:00"
}