Description

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 fb_deferred_io_state. Allocate an instance as part of initializing deferred I/O and remove it only after the final mapping has been closed. If the fb_info and the contained deferred I/O meanwhile goes away, clear struct fb_deferred_io_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.

References 7

• git.kernel.org https://git.kernel.org/stable/c/25c2b77bc463f29ee71a54b883548baf9386a0db
• git.kernel.org https://git.kernel.org/stable/c/2a40f8bc9bb713329f1c35ffc199ee961a7135b0
• git.kernel.org https://git.kernel.org/stable/c/2b53d3a52e8e5403a4f4fb57ac6cad3fd2cb1066
• git.kernel.org https://git.kernel.org/stable/c/4aab89603b637a2e441b38808c4f6fe7d1184df6
• git.kernel.org https://git.kernel.org/stable/c/4fda0d6b45faad44926dd3e4f55f118d899b2e27
• git.kernel.org https://git.kernel.org/stable/c/9ded47ad003f09a94b6a710b5c47f4aa5ceb7429
• git.kernel.org https://git.kernel.org/stable/c/a0aafb421dd15e935d81543152617f2742cefa70

Remediation