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fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages. Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs. Tested with PoC using dummy_hcd + raw_gadget USB device emulation.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.258, 5.15.209, 6.1.175, 6.12.88, 6.18.30, 6.6.140, 7.0.7
CVEs
CVE-2026-43497
Confirmed fixed CVEs
Not specified
Updated in this feed
2 Nov 2026, 17:55 UTC · Revision 1

Source evidence

fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free

core-osv · Original source

Published 21 May 2026, 12:12 UTC

In the Linux kernel, the following vulnerability has been resolved: fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages. Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs. Tested with PoC using dummy_hcd + raw_gadget USB device emulation.

osv:CVE-2026-43497

Kernel

Fixed versions: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.88, 6.18.30, 7.0.7

Complete source record
{
  "id": "097e7f97eca9b6a5e562225ca879417ee0bcc5bf050391b3421d586a7ae0b907",
  "url": "https://osv.dev/vulnerability/CVE-2026-43497",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages. Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs. Tested with PoC using dummy_hcd + raw_gadget USB device emulation.",
    "evidence": "osv:CVE-2026-43497",
    "products": [
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          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
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          {
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          }
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        "affected_versions": []
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    "severity": "high",
    "structured": {
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      "aliases": [
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      "metrics": [
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              "type": "ECOSYSTEM",
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                {
                  "introduced": "4.19.0"
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              ]
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            {
              "type": "ECOSYSTEM",
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                  "introduced": "5.11.0"
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      ],
      "modified": "2026-10-28T02:30:22.218503932Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192",
        "https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7",
        "https://git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed",
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        "https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511",
        "https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1",
        "https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6",
        "https://git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43497.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43497",
        "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/2026/43xxx/CVE-2026-43497.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43497",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 487980,
  "published_at": "2026-05-21T12:12:47.15+00:00"
}