drm/display/dp_mst: Add protection against 0 vcpi

{
  "id": "ee2b511659c99987519e26a7d5cc897a1af33190b4336a2b6da6a9791c571166",
  "url": "https://osv.dev/vulnerability/CVE-2025-71305",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "drm/display/dp_mst: Add protection against 0 vcpi",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: drm/display/dp_mst: Add protection against 0 vcpi When releasing a timeslot there is a slight chance we may end up with the wrong payload mask due to overflow if the delayed_destroy_work ends up coming into play after a DP 2.1 monitor gets disconnected which causes vcpi to become 0 then we try to make the payload = ~BIT(vcpi - 1) which is a negative shift. VCPI id should never really be 0 hence skip changing the payload mask if VCPI is 0. Otherwise it leads to <7> [515.287237] xe 0000:03:00.0: [drm:drm_dp_mst_get_port_malloc [drm_display_helper]] port ffff888126ce9000 (3) <4> [515.287267] -----------[ cut here ]----------- <3> [515.287268] UBSAN: shift-out-of-bounds in ../drivers/gpu/drm/display/drm_dp_mst_topology.c:4575:36 <3> [515.287271] shift exponent -1 is negative <4> [515.287275] CPU: 7 UID: 0 PID: 3108 Comm: kworker/u64:33 Tainted: G S U 6.17.0-rc6-lgci-xe-xe-3795-3e79699fa1b216e92+ #1 PREEMPT(voluntary) <4> [515.287279] Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER <4> [515.287279] Hardware name: ASUS System Product Name/PRIME Z790-P WIFI, BIOS 1645 03/15/2024 <4> [515.287281] Workqueue: drm_dp_mst_wq drm_dp_delayed_destroy_work [drm_display_helper] <4> [515.287303] Call Trace: <4> [515.287304] <4> [515.287306] dump_stack_lvl+0xc1/0xf0 <4> [515.287313] dump_stack+0x10/0x20 <4> [515.287316] __ubsan_handle_shift_out_of_bounds+0x133/0x2e0 <4> [515.287324] ? drm_atomic_get_private_obj_state+0x186/0x1d0 <4> [51",
    "evidence": "osv:CVE-2025-71305",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.1.165",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.128",
            "evidence": "/affected/1/ranges"
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            "value": "6.12.75",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.18.16",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.19.4",
            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-71305",
      "aliases": [
        "CVE-2025-71305"
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      "affected": [
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              "type": "ECOSYSTEM",
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                {
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-71305.json"
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      ],
      "modified": "2026-10-28T02:30:48.093715744Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/342ccffd9f77fc29fe1c05fd145e4d842bd2feaa",
        "https://git.kernel.org/stable/c/3f44cdb5371faf225af37d5caba8f21ec0572469",
        "https://git.kernel.org/stable/c/4d2ccdea18b564e3f73e3e543854acea64e6277d",
        "https://git.kernel.org/stable/c/95dbd525efce2a9e9e1c50ad15213de644c85ad0",
        "https://git.kernel.org/stable/c/ac9a7c329a5610051fc476644c9b9145a5965ecb",
        "https://git.kernel.org/stable/c/d6afc7539ce06dadfa5b4787b3cfe79b95d8f67a",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/71xxx/CVE-2025-71305.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-71305",
        "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/2025/71xxx/CVE-2025-71305.json"
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    "related_cves": [
      {
        "value": "CVE-2025-71305",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 515876,
  "published_at": "2026-05-27T12:14:55.722+00:00"
}