FKIE_CVE-2026-90095

Vulnerability from fkie_nvd - Published: 2026-09-17 17:17 - Updated: 2026-09-17 17:17
Severity
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1f59015e958174e89be58cc8db16d70a60d17255
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8f9a725d89711ad027f6b7183586ef91528f106d
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev_uring.c",
            "fs/fuse/inode.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8f9a725d89711ad027f6b7183586ef91528f106d",
              "status": "affected",
              "version": "3393ff964e0fa5def66570c54a4612bf9df06b76",
              "versionType": "git"
            },
            {
              "lessThan": "1f59015e958174e89be58cc8db16d70a60d17255",
              "status": "affected",
              "version": "3393ff964e0fa5def66570c54a4612bf9df06b76",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev_uring.c",
            "fs/fuse/inode.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.14"
            },
            {
              "lessThan": "6.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: Fix the condition to enable over-io-uring\n\nThe existing condition in fuse_uring_cmd() is there only to avoid\ndisabling io-uring for connections that already run with it, missing\nwas a condition to refuse any IORING_OP_URING_CMD if the\nconnection/channel didn\u0027t get enabled because of missing FUSE_INIT\nreply flag FUSE_OVER_IO_URING. Without the reply flag the barrier in\nfuse_uring_ready() doesn\u0027t work and IO could already be going on and\ncause deadlock states (at a minimum one between fch-\u003ebg_lock and\nqueue-\u003elock).\n\nThe change itself is trivial, but brings behavior change,\nFUSE_OVER_IO_URING has to be set in the FUSE_INIT_REPLY by fuse servers\nto accept any IORING_OP_URING_CMD. Libfuse does that and the only\nnon-libfuse implementation I found (fractal-fuse) also does it.\nQemu patches for fuse-io-uring are not merged yet, as far as I know.\n\nMoved up is the smp_load_acquire(\u0026fch-\u003einitialized) check, as a\nfuse-server implementation might try to setup io-uring before FUSE_INIT\nis processed and might have gotten -EOPNOTSUPP instead of -EAGAIN.\n\nAlso fixed is a stale comment that explains the handling of the\nFUSE_OVER_IO_URING flag in early RFC versions.\n\nIf there should be a report from any library or application we\nprobably need to revert this commit."
    }
  ],
  "id": "CVE-2026-90095",
  "lastModified": "2026-09-17T17:17:01.123",
  "metrics": {},
  "published": "2026-09-17T17:17:01.123",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1f59015e958174e89be58cc8db16d70a60d17255"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8f9a725d89711ad027f6b7183586ef91528f106d"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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