AZL-88514

In the Linux kernel, the following vulnerability has been resolved:

fbdev: defio: Disconnect deferred I/O from the lifetime of struct fb_info

Hold state of deferred I/O in struct fbdeferrediostate. Allocate an instance as part of initializing deferred I/O and remove it only after the final mapping has been closed. If the fbinfo and the contained deferred I/O meanwhile goes away, clear struct fbdeferredio_state.info to invalidate the mapping. Any access will then result in a SIGBUS signal.

Fixes a long-standing problem, where a device hot-unplug happens while user space still has an active mapping of the graphics memory. The hot- unplug frees the instance of struct fb_info. Accessing the memory will operate on undefined state.