CVE-2026-97996virtio: fix use-after-free in unregister_virtio_device()

Official description

In the Linux kernel, the following vulnerability has been resolved: virtio: fix use-after-free in unregister_virtio_device() device_unregister() is device_del() plus put_device(). When the caller holds no extra reference, that drops the last one and runs the release callback, which for several transports frees the memory the embedded struct virtio_device sits in. unregister_virtio_device() then calls virtio_debug_device_exit(), which reads dev->debugfs_dir out of the freed object. Affected transports are the ones whose release callback frees and whose remove path takes no reference: virtio_mmio, virtio_vdpa, virtio_uml, mlxbf-tmfifo and virtio_ccw. virtio_pci is unaffected because virtio_pci_remove() brackets the call with get_device() and put_device(). Remove the debugfs entries before the device can go away. They are only accessed through the protected debugfs interface, so debugfs_remove_recursive() waits for in-progress file operations before returning. Tearing them down while the device is still alive is therefore safe. Reproduced on User-Mode Linux with CONFIG_KASAN and CONFIG_VIRTIO_DEBUG by unbinding a virtio-uml device: BUG: KASAN: slab-use-after-free in virtio_debug_device_exit+0x36/0x4d Read of size 8 at addr 00000000616e0b10 by task init/1 __asan_report_load8_noabort virtio_debug_device_exit+0x36/0x4d unregister_virtio_device+0x48/0x75 virtio_uml_remove platform_remove device_release_driver_internal unbind_store Freed by task 1: kfree virtio_uml_release_dev device_release kobject_put put_device device_unregister With this applied, the report is gone and unbind is clean.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/951cad50cba89e736afdee4a730e0e52f9245c9b
• https://git.kernel.org/stable/c/77dbd10a701a30fdfea5c3bb7a29163128f9a9c7
• https://git.kernel.org/stable/c/caf042153016d651b55d0fb4a63cdf7d0d23dee2
• https://git.kernel.org/stable/c/3f9a0fceb730f5107d52421ead5568eae25a0049