On December 2023, a serious bug in the Linux kernel was assigned CVE-2023-52647. It impacts the NXP iMX8-ISI (Image Signal Interface) driver within Linux’s media subsystem. If you’re running recent Linux on ARM hardware (like NXP i.MX8 platforms), this is relevant. Here’s everything you need to know.

What Is CVE-2023-52647?

The i.MX8 is an advanced system-on-chip (SoC) widely used in automotive, industrial, and multimedia products.

The ISI driver in the Linux kernel connects camera sensors and video devices using a "crossbar"—think of this as a virtual switchboard for video streams. In older code, there wasn’t enough checking to confirm that pads (links in the pipeline) actually existed before trying to use them.

The Core Problem

- The driver could dereference a NULL pointer when userspace tried to enable a camera/video stream that ended at an unconnected crossbar sink.

Example of the Bug

// media/nxp/imx8-isi/mx8-isi-cap.c (simplified)
struct v4l2_subdev *remote_sd;
struct media_pad *remote_pad;
...
remote_pad = media_entity_remote_pad(pad);
...
remote_sd = media_entity_to_v4l2_subdev(remote_pad->entity);  // CRASH if remote_pad is NULL!

No check was done on remote_pad before accessing it.

Who Can Exploit This?

- Any user on the system with access to the media device (e.g., /dev/video*)
- A malicious program could repeatedly set up a streaming pipeline to a non-existent pad until the system crashes.

Example Attack (Conceptual)

# Using v4l2-ctl, user sets up a video pipeline ending at an unused sink
v4l2-ctl --set-dv-bt-timings query --device /dev/video
# If /dev/video is unconnected, the old driver could crash here

Or custom C code that constructs bogus V4L2 pipelines will do the same.

Result: Crashes kernel, all users lose access, may cause data loss.

The Fix

Kernel developers patched this in mainline commit c0461eae39e3.

They added a safety check

remote_pad = media_entity_remote_pad(pad);
if (!remote_pad) {
    // Return error if the connection isn't valid
    dev_err(isi->dev, "No remote pad on sink: %d\n", pad->index);
    return -EINVAL;
}
remote_sd = media_entity_to_v4l2_subdev(remote_pad->entity); // Safe now

Now, if the pad doesn't exist, the driver prints an error and returns—no crash!

References and More Reading

- Official kernel patch
- CVE-2023-52647 at NVD
- Linux v4l2 documentation

2. Restrict access to /dev/video\* to trusted users.

Summary

*CVE-2023-52647* shows that unchecked pointers can have big security impacts, even in obscure hardware drivers. Modern Linux kernels get better every day thanks to checks like these. If you use NXP iMX8 for video, patch now to stay safe!

Timeline

Published on: 05/01/2024 06:15:06 UTC
Last modified on: 05/04/2025 07:40:48 UTC