FKIE_CVE-2026-43497

Vulnerability from fkie_nvd - Published: 2026-05-21 13:16 - Updated: 2026-05-21 13:16
Severity ?
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6
Impacted products
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free\n\ndlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages\nto userspace but sets no vm_ops on the VMA. This means the kernel cannot\ntrack active mmaps. When dlfb_realloc_framebuffer() replaces the backing\nbuffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated.\nOn USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages\nwhile userspace PTEs still reference them, resulting in a use-after-free:\nthe process retains read/write access to freed kernel pages.\n\nAdd vm_operations_struct with open/close callbacks that maintain an\natomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(),\ncheck mmap_count and return -EBUSY if the buffer is currently mapped,\npreventing buffer replacement while userspace holds stale PTEs.\n\nTested with PoC using dummy_hcd + raw_gadget USB device emulation."
    }
  ],
  "id": "CVE-2026-43497",
  "lastModified": "2026-05-21T13:16:19.090",
  "metrics": {},
  "published": "2026-05-21T13:16:19.090",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}


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