CVE-2026-90044 (GCVE-0-2026-90044)
Vulnerability from cvelistv5
Published
2026-09-16 10:33
Modified
2026-10-21 12:49
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Fix Use-After-Free in AIO error path In ffs_epfile_write_iter() and ffs_epfile_read_iter(), when ffs_epfile_io() fails with an error other than -EIOCBQUEUED, the io_data structure (`p`) is freed. However, for AIO operations, the kiocb cancel function was already armed and kiocb->private was set to `p`. If a concurrent cancel operation (such as sys_io_cancel()) executes after ffs_epfile_io() fails but before the function frees `p`, a Use-After-Free can occur when the cancellation handler accesses the freed pointer. To securely fix this race condition, we must properly un-arm the cancellation. Invoking `kiocb->ki_complete()` does exactly this by acquiring `ctx->ctx_lock` and safely removing the kiocb from the active sequence. In doing so, it ensures that a parallel io_cancel can no longer discover the kiocb, effectively closing the race window. We then return -EIOCBQUEUED to notify the VFS layer that the kiocb has been consumed and it should avoid attempting to complete the request again or triggering subsequent completion handlers.
References
Impacted products
Vendor Product Version
Linux Linux Version: de2080d41b5d584205e408d72021f0f335a046fc
Version: de2080d41b5d584205e408d72021f0f335a046fc
Version: de2080d41b5d584205e408d72021f0f335a046fc
Version: de2080d41b5d584205e408d72021f0f335a046fc
Version: de2080d41b5d584205e408d72021f0f335a046fc
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
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          "vendor": "Linux",
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              "version": "0",
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              "version": "7.2.5",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.160",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Fix Use-After-Free in AIO error path\n\nIn ffs_epfile_write_iter() and ffs_epfile_read_iter(), when ffs_epfile_io()\nfails with an error other than -EIOCBQUEUED, the io_data structure (`p`) is\nfreed. However, for AIO operations, the kiocb cancel function was already\narmed and kiocb-\u003eprivate was set to `p`.\n\nIf a concurrent cancel operation (such as sys_io_cancel()) executes after\nffs_epfile_io() fails but before the function frees `p`, a Use-After-Free\ncan occur when the cancellation handler accesses the freed pointer.\n\nTo securely fix this race condition, we must properly un-arm the\ncancellation. Invoking `kiocb-\u003eki_complete()` does exactly this by\nacquiring `ctx-\u003ectx_lock` and safely removing the kiocb from the active\nsequence. In doing so, it ensures that a parallel io_cancel can no longer\ndiscover the kiocb, effectively closing the race window.\n\nWe then return -EIOCBQUEUED to notify the VFS layer that the kiocb has been\nconsumed and it should avoid attempting to complete the request again or\ntriggering subsequent completion handlers."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is in FunctionFS epfile AIO (`ffs_epfile_write_iter`/`read_iter` via `io_submit`/`io_cancel` on functionfs ep files), a local syscall path. `ffs_epfile_io()` can fail with `-EAGAIN` on `O_NONBLOCK` before any USB host is involved; this is the gadget userspace API, matching CVE-2024-36894/CVE-2026-63894 as Local rather than Physical.\nAC:L - The attacker controls both sides: one thread `io_submit`s AIO that fails after `kiocb_set_cancel_fn` (O_NONBLOCK `-EAGAIN`, halt, `-EFAULT`), while another calls `io_cancel`/`io_destroy`. The race between `kfree(p)` and `aio_remove_iocb` is freely retryable, so a race the attacker creates is AC:L.\nPR:L - FunctionFS mounts commonly use `uid=`/`gid=`/`fmode=` to delegate ep files to unprivileged gadget daemons (adbd/shell on Android, MTP, embedded USB services). Once mounted by init, those accounts can open ep files and issue AIO without init-namespace root.\nUI:N - The attacker performs `io_submit` and `io_cancel`/`io_destroy` on their own FunctionFS endpoint fds. No separate victim action is required beyond an already-deployed FunctionFS gadget.\nS:U - The use-after-free corrupts kernel heap (`ffs_io_data`) within the same host kernel security authority. This is ordinary local privilege escalation, not a VM escape or IOMMU/sandbox boundary cross.\nC:H - Use-after-free of `ffs_io_data`: `ffs_aio_cancel()` reads `kiocb-\u003eprivate` after `kfree`. Reclaim of that kmalloc object lets the attacker control `io_data-\u003eep`/`req` and leak kernel memory via UDC dequeue; UAFs are scored High for confidentiality.\nI:H - A reclaimed `ffs_io_data` yields attacker-controlled pointers passed to `usb_ep_dequeue()` from `ffs_aio_cancel`, providing a heap write and control-flow hijack primitive. Kernel UAFs are scored High for integrity.\nA:H - Dereferencing the freed `ffs_io_data` in `ffs_aio_cancel` causes kernel oops/panic even without a full exploit; any such crash is High availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:49:36.628Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0a2f71ccf9c2053de725e9a7922d081f3f3a3804"
        },
        {
          "url": "https://git.kernel.org/stable/c/b5f0e80a03e87bd932487e03248eae3ba3ed7b45"
        },
        {
          "url": "https://git.kernel.org/stable/c/153b5ecd29ed055562400bc17c91df3fd869b0ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/4a2fb2d12b87b43724230abb52a1440617c7b6cc"
        },
        {
          "url": "https://git.kernel.org/stable/c/e78dcb1f7ec271449c54984dc90c62a5ba272de7"
        }
      ],
      "title": "usb: gadget: f_fs: Fix Use-After-Free in AIO error path",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90044",
    "datePublished": "2026-09-16T10:33:41.695Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-10-21T12:49:36.628Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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