{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-97931",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-97931"
  ],
  "published": "2026-09-25T10:24:31Z",
  "summary": "ALSA: us122l: Prevent write upgrades for read mappings",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: us122l: Prevent write upgrades for read mappings\n\nThe hwdep mmap callback rejects read-buffer mappings that are initially\nwritable, but leaves VM_MAYWRITE set on mappings created with PROT_READ.\nA process that can open the hwdep node O_RDWR can later use mprotect() to\nmake the mapping writable.\n\nThe read allocation begins with struct usb_stream. Its read_size member is\nused by the fault handler to decide which pages belong to the read buffer.\nThe read VMA intentionally remains expandable because pcm_usb_stream uses\nmremap() after reading that size. Changing read_size first can therefore\nmap and access pages beyond the allocation. The same member is also\nconsumed by usb_stream_free(), where changing it can make\nfree_pages_exact() release pages outside the allocation.\n\nClear VM_MAYWRITE for read-buffer mappings after rejecting an initially\nwritable VMA. This keeps the separate output-buffer mapping writable while\npreventing later permission upgrades.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.189",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-97931"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cbc1f954ce67d739d41d1f0757d29850353ebb6a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/becb89036a1320ef0a77da2d27935ac0704345c4"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6a5f5a5a32c78e67701f1d0f26bc87af68895604"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/938e8d6cee8d36f24669dfdcd3717e081eb32d64"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/64a87950239867682cde128020e1a47088295e5c"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d9c537b14f4982f17b103e3a2cfeee4bee6bc026"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/71c610aeb1770302ac9c9e0b9a4ecd37f1311928"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-10-03T11:04:09Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.0,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The bad data is written by a local process. It maps the us122l hwdep read buffer PROT_READ via usb_stream_hwdep_mmap(), upgrades it with mprotect() because VM_MAYWRITE was never cleared, and overwrites usb_stream.read_size. No remote protocol or USB packet carries the malicious value.\nAC:H - The driver only binds, and only creates /dev/snd/hwC*D*, when a TASCAM US-122L/US-144 is attached. A local attacker can't produce that hardware without physical access. Once it is present, mmap, mprotect, a read_size overwrite and mremap are fully deterministic.\nPR:L - The attacker needs an O_RDWR open of the hwdep node, which a normal user gets through audio group or seat uaccess ACLs. usb_stream_hwdep_open() and usb_stream_hwdep_ioctl() do no capability checks, and the stream already exists from probe.\nUI:N - The attacker's own process does the open, mmap, mprotect, write to read_size, mremap and page faults. No other user has to act.\nS:U - The result is corrupted kernel memory and local privilege escalation within the same kernel authority. No VM or hardware isolation boundary is crossed.\nC:H - With an inflated read_size, usb_stream_hwdep_vm_fault() maps virt_to_page((char *)s + offset) for offsets past the alloc_pages_exact() buffer. Userspace can then directly read arbitrary adjacent kernel pages.\nI:H - Those out-of-bounds pages are mapped writable into userspace, giving direct write access to kernel memory. In addition, usb_stream_free() calls free_pages_exact(s, read_size) with the tampered size, freeing pages that are still in use, a page-level use-after-free.\nA:H - Writing to foreign kernel pages, or freeing the wrong pages through usb_stream_free() on SET_PARAMS re-init or disconnect, corrupts the page allocator and kernel data, which leads to an oops or panic."
    }
  }
}