CVE-2026-43497

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