CVE-2023-52465: Linux Kernel Power Supply Module Vulnerability - Revisiting smb2

The Linux kernel is the foundation of every Linux-based system, and any vulnerability within the kernel can pose a significant risk to the security and stability of the system. As a result, it is essential for users to stay up to date with the latest patches and releases to avoid any major issues. One such vulnerability that has recently been patched is CVE-2023-52465, dealing with a null pointer dereference within the power supply module of the Linux kernel. This long-read post will provide an in-depth discussion of this vulnerability's causes, a code snippet showcasing the fix, and original references to further understand the issue and the applied patch.

Exploit Details

CVE-2023-52465 is a vulnerability in the power supply module of the Linux kernel, specifically in the function smb2_probe. This function is responsible for initializing the smb2 device and allocates memory using the devm_kasprintf and devm_kzalloc functions. These functions return a pointer to the newly allocated memory, which can be NULL if the allocation has failed.

The vulnerability arises due to the lack of proper NULL pointer checks in the code. If either of these functions fails to allocate memory and returns NULL, the subsequent code using these pointers would lead to a null pointer dereference, causing the kernel to crash. This could potentially be exploited by an attacker to cause a denial of service (DoS) on the affected system.

Fix Details and Code Snippet

The patch that resolves this vulnerability (CVE-2023-52465) has been developed and submitted by Linux kernel developers. The fix is relatively simple and consists of adding proper NULL pointer checks to the smb2_probe function in the power supply module. This will prevent the kernel from crashing when memory allocation for the smb2 device fails.

Here's a code snippet showcasing the fix in the smb2_probe function

 static int smb2_probe(struct i2c_client *client,
                      const struct i2c_device_id *id)
 {
     struct smb2 *smb;
     int ret;
 
     smb = devm_kzalloc(&client->dev, sizeof(*smb), GFP_KERNEL);
     if (!smb)
         return -ENOMEM;
 
     smb->dev = &client->dev;
 
     mutex_init(&smb->wrkr_lock);
 
     smb->version = id->driver_data;
 
     smb->id_string = devm_kasprintf(&client->dev, GFP_KERNEL,
                                     "smb%d", id->driver_data);
     if (!smb->id_string)
         return -ENOMEM;
 
    // ... rest of the code
 }

With this fix, if either devm_kasprintf or devm_kzalloc returns NULL, the function will return an error (-ENOMEM) instead of causing a null pointer dereference. This prevents the kernel crash and closes the vulnerability.

Original References

For those interested in more detailed information on the Linux kernel source code and the patch that was submitted, you can refer to the following sources:

- Linux Kernel Bugzilla Report - The original bug report which discusses the issue at length.

- Linux Kernel Mailing List Patch - The accepted patch to the Linux kernel source code that resolves this vulnerability.

Conclusion

In conclusion, CVE-2023-52465 is a vulnerability in the Linux kernel's power supply module. The lack of proper NULL pointer checks in the smb2_probe function could cause a kernel crash and potentially be exploited by an attacker for a denial of service attack. If you are running a Linux-based system, it is crucial to stay informed about these vulnerabilities and ensure your kernel is up-to-date with the latest security patches. By doing so, you can better protect your system and data from potential exploits.

Timeline

Published on: 02/26/2024 16:27:48 UTC
Last modified on: 04/17/2024 19:16:10 UTC