CVE-2019-18683: Exploiting a Linux kernel vulnerability in the V4L2 subsystem

This article discloses exploitation of CVE-2019-18683, which refers to multiple five-year-old race conditions in the V4L2 subsystem of the Linux kernel. I found and fixed them at the end of 2019. I gave a talk at OffensiveCon 2020 about it (slides).

Here I'm going to describe a PoC exploit for x86_64 that gains local privilege escalation from the kernel thread context (where the userspace is not mapped), bypassing KASLR, SMEP, and SMAP on Ubuntu Server 18.04.

Intel x86 Root of Trust: loss of trust

The scenario that Intel system architects, engineers, and security specialists perhaps feared most is now a reality. A vulnerability has been found in the ROM of the Intel Converged Security and Management Engine (CSME). This vulnerability jeopardizes everything Intel has done to build the root of trust and lay a solid security foundation on the company's platforms. The problem is not only that it is impossible to fix firmware errors that are hard-coded in the Mask ROM of microprocessors and chipsets. The larger worry is that, because this vulnerability allows a compromise at the hardware level, it destroys the chain of trust for the platform as a whole.

Positive Technologies specialists have discovered an error in Intel hardware, as well as an error in Intel CSME firmware at the very early stages of the subsystem's operation, in its boot ROM. Intel CSME is responsible for initial authentication of Intel-based systems by loading and verifying all other firmware for modern platforms. For instance, Intel CSME interacts with CPU microcode to authenticate UEFI BIOS firmware using BootGuard. Intel CSME also loads and verifies the firmware of the Power Management Controller responsible for supplying power to Intel chipset components.