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

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Summary

CVECVE-2026-43497
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-21 13:16:19 UTC
Updated2026-06-26 17:29:05 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.3 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

EPSS: 0.000120000 probability, percentile 0.018840000 (date 2026-06-04)

Problem Types: CWE-416

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
3.1CNADECLARED7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd 60f711cfd580f86fea8284146ac133804e728f9a git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd 5931f5651ee32bd41b3323256b31fcc8e71336ed git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd e3d9865dacd7435b8465848428210d0f0c673311 git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd 4f312c30f0368e8d2a76aa650dff73f23490b5e7 git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd 18dd358de72d57993422cbb5dfb29ccd74efe192 git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd da9b065cedfd3b574f229d5be594e6aa47a27ae6 git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd a2c53a3822ee26e8d758071815b9ed3bf6669fc1 git Not specified
CNA Linux Linux affected 7433914efd584b22bb49d3e1eee001f5d0525ecd 8de779dc40d35d39fa07387b6f921eb11df0f511 git Not specified
CNA Linux Linux affected 4.19 Not specified
CNA Linux Linux unaffected 4.19 semver Not specified
CNA Linux Linux unaffected 5.10.258 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.209 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.140 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.88 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.30 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.7 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/60f711cfd580f86fea8284146ac133804e728f9a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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