drm/ttm: Account for NULL and handle pages in ttm_pool_backup

{
  "id": "185a71af90b434061809951944452bf8f0b6574015634e52b12536acee678432",
  "url": "https://osv.dev/vulnerability/CVE-2026-68239",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "drm/ttm: Account for NULL and handle pages in ttm_pool_backup",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: drm/ttm: Account for NULL and handle pages in ttm_pool_backup Pages in ttm_pool_backup can be NULL or backup handles (ttm_backup_page_ptr_is_handle()), neither of which can be passed to set_pages_array_wb() or freed. Add a dedicated WB pass before the dma/purge loop that walks allocations using the same i += num_pages stride, skipping NULL and handle entries, and calls set_pages_array_wb() once per contiguous run of real pages. Apply the same NULL/handle guard to the dma/purge loop. Fixes the following oops: Oops: general protection fault, kernel NULL pointer dereference 0x0: 0000 [#1] SMP NOPTI RIP: 0010:__cpa_process_fault+0xf8/0x770 RSP: 0018:ffffc90000a87718 EFLAGS: 00010287 RAX: 0000000000000000 RBX: ffffc90000a87868 RCX: 0000000000000000 RDX: 0000000000001000 RSI: 0005088000000000 RDI: ffffffff827c5f34 RBP: 0005088000000000 R08: ffffc90000a877cb R09: ffffc90000a877d0 R10: 0000000000000000 R11: 000000000000001b R12: 000ffffffffff000 R13: ffffc90000a87868 R14: ffffc90000a87868 R15: ffff88815b882ae0 FS: 0000000000000000(0000) GS:ffff8884ec840000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f930b844000 CR3: 000000000262e003 CR4: 0000000008f70ef0 PKRU: 55555554 Call Trace: __change_page_attr_set_clr+0x989/0xe90 ? __purge_vmap_area_lazy+0x6c/0x3a0 ? _vm_unmap_aliases+0x250/0x2a0 set_pages_array_wb+0x7f/0x120 ttm_pool_backup+0x4c9/0x5b0 [ttm] ? dma_resv_wait_timeout+0",
    "evidence": "osv:CVE-2026-68239",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.42",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-68239",
      "aliases": [
        "CVE-2026-68239"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "b63d715b8090aed48bdef5930625946fa4c0d324"
                },
                {
                  "fixed": "22aa7fb4e7d0b3ab41d1240ed743167980912970"
                },
                {
                  "fixed": "9ddaabf38f7a45b329e34358b98d2968d8649d21"
                },
                {
                  "fixed": "5b7b3b6595ee77d01c7463757baed114786094dd"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68239.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.15.0"
                },
                {
                  "fixed": "6.18.42"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68239.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.146352087Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/22aa7fb4e7d0b3ab41d1240ed743167980912970",
        "https://git.kernel.org/stable/c/5b7b3b6595ee77d01c7463757baed114786094dd",
        "https://git.kernel.org/stable/c/9ddaabf38f7a45b329e34358b98d2968d8649d21",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68239.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-68239",
        "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/2026/68xxx/CVE-2026-68239.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-68239",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 509097,
  "published_at": "2026-08-10T12:01:04.297+00:00"
}