fuse: Fix the condition to enable over-io-uring

{
  "id": "9670aa7fab8a45528e59a32efce58c25e4f494e732f52b5774c0fa52c37ec4f6",
  "url": "https://osv.dev/vulnerability/CVE-2026-90095",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fuse: Fix the condition to enable over-io-uring",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fuse: Fix the condition to enable over-io-uring The existing condition in fuse_uring_cmd() is there only to avoid disabling io-uring for connections that already run with it, missing was a condition to refuse any IORING_OP_URING_CMD if the connection/channel didn't get enabled because of missing FUSE_INIT reply flag FUSE_OVER_IO_URING. Without the reply flag the barrier in fuse_uring_ready() doesn't work and IO could already be going on and cause deadlock states (at a minimum one between fch->bg_lock and queue->lock). The change itself is trivial, but brings behavior change, FUSE_OVER_IO_URING has to be set in the FUSE_INIT_REPLY by fuse servers to accept any IORING_OP_URING_CMD. Libfuse does that and the only non-libfuse implementation I found (fractal-fuse) also does it. Qemu patches for fuse-io-uring are not merged yet, as far as I know. Moved up is the smp_load_acquire(&fch->initialized) check, as a fuse-server implementation might try to setup io-uring before FUSE_INIT is processed and might have gotten -EOPNOTSUPP instead of -EAGAIN. Also fixed is a stale comment that explains the handling of the FUSE_OVER_IO_URING flag in early RFC versions. If there should be a report from any library or application we probably need to revert this commit.",
    "evidence": "osv:CVE-2026-90095",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.57",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-90095",
      "aliases": [
        "CVE-2026-90095"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "3393ff964e0fa5def66570c54a4612bf9df06b76"
                },
                {
                  "fixed": "1ca1df82d9248fc0b5ff17d45607484f18e5d60b"
                },
                {
                  "fixed": "8f9a725d89711ad027f6b7183586ef91528f106d"
                },
                {
                  "fixed": "1f59015e958174e89be58cc8db16d70a60d17255"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90095.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.14.0"
                },
                {
                  "fixed": "6.18.57"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90095.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:45.314831374Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1ca1df82d9248fc0b5ff17d45607484f18e5d60b",
        "https://git.kernel.org/stable/c/1f59015e958174e89be58cc8db16d70a60d17255",
        "https://git.kernel.org/stable/c/8f9a725d89711ad027f6b7183586ef91528f106d",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90095.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-90095",
        "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/2026/90xxx/CVE-2026-90095.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-90095",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 513427,
  "published_at": "2026-09-17T16:06:08.197+00:00"
}