CVE-2026-97952 (GCVE-0-2026-97952)
Vulnerability from cvelistv5
Published
2026-09-25 10:23
Modified
2026-10-19 09:11
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: sunvdc: unmap LDC cookies when the descriptor send fails __send_request() maps the request's pages into the LDC channel's map table (ldc_map_sg()), fills in the descriptor and marks it VIO_DESC_READY before ringing the doorbell via __vdc_tx_trigger(). When the trigger fails, the error path only prints a message: the descriptor stays READY and the cookies are never unmapped. The mapping is normally released in vdc_end_one() when the peer completes the descriptor - but a descriptor whose doorbell was never sent will never complete, and since dr->prod is not advanced on failure, the reset path (vdc_requeue_inflight(), which walks [cons, prod)) never visits it either. The map table entries are leaked permanently. Since commit a11f6ca9aef9 ("sunvdc: Do not spin in an infinite loop when vio_ldc_send() returns EAGAIN") trigger failures occur in practice under load, so every resulting I/O error also leaks one request's worth of entries from the fixed-size (8192 entries per channel) map table. Because the allocator hands out contiguous ranges, fragmentation makes large multi-segment requests fail first as the table drains, until ldc_map_sg() fails permanently and the disk is dead until reboot. It also makes any retry-based recovery unusable: requeuing the request on -EAGAIN remaps the pages on every attempt, overwriting desc->cookies and orphaning the previous mapping, so the table drains at the retry rate. This is the memory exhaustion observed when the requeue approach was first tested in October 2025. Roll back on failure: unmap the cookies, mark the descriptor FREE again and clear the request entry. If the trigger failed with -ENOTCONN, __vdc_tx_trigger() has already reset the port, which tears down and reallocates both the dring and the LDC channel including its map table - nothing to roll back, and the stale descriptor must not be touched.
References
Impacted products
Vendor Product Version
Linux Linux Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec
Version: 627e656239c63d8a81672d08de7885e89c12fa75
Version: a1ef7d5da9b2c145f811a80bb8197df6037a7572
Version: 7ab4b6526fdcdfa7772984bbcd2ac4fd14fa223b
Version: 3fbba4e55051d01a72b56ea192064175924bf56a
Version: 3e380fc2ae4d18210eec9c472b12e2b2544f7dc1
Version: 4.4.175   ≤
Version: 4.9.156   ≤
Version: 4.14.99   ≤
Version: 4.19.21   ≤
Version: 4.20.8   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsunvdc: unmap LDC cookies when the descriptor send fails\n\n__send_request() maps the request\u0027s pages into the LDC channel\u0027s map\ntable (ldc_map_sg()), fills in the descriptor and marks it\nVIO_DESC_READY before ringing the doorbell via __vdc_tx_trigger().\nWhen the trigger fails, the error path only prints a message: the\ndescriptor stays READY and the cookies are never unmapped. The\nmapping is normally released in vdc_end_one() when the peer completes\nthe descriptor - but a descriptor whose doorbell was never sent will\nnever complete, and since dr-\u003eprod is not advanced on failure, the\nreset path (vdc_requeue_inflight(), which walks [cons, prod)) never\nvisits it either. The map table entries are leaked permanently.\n\nSince commit a11f6ca9aef9 (\"sunvdc: Do not spin in an infinite loop\nwhen vio_ldc_send() returns EAGAIN\") trigger failures occur in\npractice under load, so every resulting I/O error also leaks one\nrequest\u0027s worth of entries from the fixed-size (8192 entries per\nchannel) map table. Because the allocator hands out contiguous\nranges, fragmentation makes large multi-segment requests fail first\nas the table drains, until ldc_map_sg() fails permanently and the\ndisk is dead until reboot.\n\nIt also makes any retry-based recovery unusable: requeuing the\nrequest on -EAGAIN remaps the pages on every attempt, overwriting\ndesc-\u003ecookies and orphaning the previous mapping, so the table\ndrains at the retry rate. This is the memory exhaustion observed\nwhen the requeue approach was first tested in October 2025.\n\nRoll back on failure: unmap the cookies, mark the descriptor FREE\nagain and clear the request entry. If the trigger failed with\n-ENOTCONN, __vdc_tx_trigger() has already reset the port, which\ntears down and reallocates both the dring and the LDC channel\nincluding its map table - nothing to roll back, and the stale\ndescriptor must not be touched."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:11:18.495Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/eb9c5f6747fe98b83c78cb5476a914e91d50e8e8"
        },
        {
          "url": "https://git.kernel.org/stable/c/24564576be423f3b5d7e67cd7df848ac66646497"
        },
        {
          "url": "https://git.kernel.org/stable/c/9251573e7cf7d797ae4a30b2a236af8242237a61"
        },
        {
          "url": "https://git.kernel.org/stable/c/b0de6463667e9bb9dc14a83a9c24c1b6b3f7b5f7"
        },
        {
          "url": "https://git.kernel.org/stable/c/ab81a5c1014a38dab0fb402609fd866b0bcb4726"
        },
        {
          "url": "https://git.kernel.org/stable/c/57835952566f0be9b365a6eb3a70b397a9d5ef47"
        },
        {
          "url": "https://git.kernel.org/stable/c/f3322baa3a8ac87730feae952c1146269d78e098"
        },
        {
          "url": "https://git.kernel.org/stable/c/0c6da21fa35e03fc74f09895433ccd6d4a9c3530"
        }
      ],
      "title": "sunvdc: unmap LDC cookies when the descriptor send fails",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97952",
    "datePublished": "2026-09-25T10:23:00.161Z",
    "dateReserved": "2026-09-25T10:18:58.205Z",
    "dateUpdated": "2026-10-19T09:11:18.495Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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