CVE-2024-26963 is a recently patched vulnerability in the Linux kernel affecting the dwc3-am62 USB controller driver. If you rely on ARM-based devices or single-board computers running recent Linux kernels (like some TI AM62x boards), this bug and its fix are directly relevant to you — especially if you ever hotplug, module reload, or tinker with USB host drivers.
Let's break down the issue in real-world terms, look at the technical core, and show some code and references so you can understand or even experiment (safely!) with this scenario.
What is the Vulnerability?
In Linux, device drivers often exist as kernel modules. The dwc3-am62 USB module manages hardware for certain boards. The vulnerability here isn’t remote code execution or privilege escalation, but bad module handling: specifically, unsafe behavior when unloading and reloading the driver.
The Problem
The module enables Runtime Power Management (runtime PM) by default. This means the hardware can go to sleep (be "suspended") when not in use to save energy. However, when you remove (rmmod) the module, the removal routine could find the device suspended—which is dangerous if you start directly poking or disabling hardware registers that might no longer be live.
If the driver tried to disable a clock that was already off, you’d get a kernel warning
[ 39.705310] ------------[ cut here ]------------
[ 39.710004] clk:162:3 already disabled
[ 39.713941] WARNING: CPU: PID: 921 at drivers/clk/clk.c:109 clk_core_disable+xb/xb8
Worse, the driver didn’t pair its initialization and cleanup routines correctly, sometimes breaking module reload.
It forces the device to resume (wake up) on module removal
This is done using pm_runtime_get_sync() right at the start of .remove() to ensure the hardware is awake before doing anything else.
(No double-disable, so no kernel warnings).
Rather than manually reversing all init steps, it calls the correct platform cleanup (of_platform_depopulate()), avoiding reload issues or memory leaks.
Code Snippet – The Key Part
The crucial fix looks something like this (from the official patch):
static int dwc3_am62_remove(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
// Make sure device is awake before access
pm_runtime_get_sync(dev);
// Clean up any platform-created devices
of_platform_depopulate(dev);
// Mark device as unused and allow suspension
pm_runtime_put_sync(dev);
return ;
}
Compare this to the buggy version, which didn’t do the power management handshake, nor called the correct cleanup.
Reproducing and (Safely) Exploiting the Bug
If you’re running a vulnerable kernel, you can observe (not exploit for malicious purposes!) the problematic behavior like this:
`
On certain platforms, USB might break or act weird, and sometimes the device won’t re-enumerate properly until a reboot.
Why does this matter?
- Unprivileged processes could possibly trigger kernel warnings (denial-of-service vector on strict systems).
- Repeated module reloads could destabilize your system or break device enumeration—bad in embedded/IoT environments.
Official kernel patch:
Linux commit 7e1eebe037d85c3602deef381e3afb5edca7e383
Linux kernel bug discussion:
Runtime PM documentation:
Bottom Line
CVE-2024-26963 shows how even “safe” paths (like power-saving features or kernel module reloads) can combine to produce dangerous, system-wrecking bugs. While there’s no remote attack possible, a user or script with enough privileges could cause kernel warnings, resource leaks, and USB driver chaos.
Upgrade your kernel if you use ARM boards with TI AM62x and similar chips, or backport the patch if you maintain an older branch.
If you want to hack, experiment, or help upstream, always test on non-production devices!
Timeline
Published on: 05/01/2024 06:15:12 UTC
Last modified on: 05/04/2025 09:00:55 UTC