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.
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No vendor fix or workaround currently provided.
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Mon, 01 Jun 2026 17:00:00 +0000
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Sat, 30 May 2026 11:00:00 +0000
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| Metrics |
cvssV3_1
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Fri, 22 May 2026 02:15:00 +0000
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| Weaknesses | CWE-416 |
Fri, 22 May 2026 00:15:00 +0000
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| Weaknesses | CWE-825 | |
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Thu, 21 May 2026 13:45:00 +0000
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| Weaknesses | CWE-416 |
Thu, 21 May 2026 12:30:00 +0000
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| Description | 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. | |
| Title | fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free | |
| First Time appeared |
Linux
Linux linux Kernel |
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| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
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| References |
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Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-06-14T17:45:29.664Z
Reserved: 2026-05-01T14:12:56.013Z
Link: CVE-2026-43497
No data.
Status : Awaiting Analysis
Published: 2026-05-21T13:16:19.090
Modified: 2026-06-17T10:49:49.063
Link: CVE-2026-43497
OpenCVE Enrichment
Updated: 2026-05-30T13:15:24Z