CVE-2023-52450 - Fixing a NULL Pointer Dereference Vulnerability in the Linux Kernel's perf/x86/intel/uncore Subsystem

A security vulnerability (CVE-2023-52450) has been recently discovered and fixed in the Linux kernel. The vulnerability resides in the kernel's perf/x86/intel/uncore subsystem. In this post, we will discuss the details of this vulnerability, how it can be exploited, and what the Linux kernel developers have done to mitigate the problem. We will also provide a code snippet and relevant links to the original references for a better understanding.

Background

The Linux kernel's perf/x86/intel/uncore subsystem is responsible for managing performance counters that provide information about various aspects of the hardware's performance. This can be helpful in understanding system bottlenecks, optimizing code, and performing other performance profiling tasks.

The Vulnerability (CVE-2023-52450)

The vulnerability was caused by a NULL pointer dereference issue in the upi_fill_topology() function. Essentially, this NULL pointer dereference occurred due to an out-of-bound access on the following line:

upi = &type->topology[nid][idx];

This line was attempting to access an invalid memory location, leading to the NULL pointer dereference. To fix this issue, the Linux kernel developers changed the code to get the logical socket id instead of the physical id in the discover_upi_topology() function. This prevents the out-of-bound access and, ultimately, the NULL pointer dereference in upi_fill_topology().

The Exploit Details

Considering the NULL pointer dereference vulnerability, a potential attacker may be able to exploit this issue by crafting specific input data that triggers the out-of-bound access in the kernel code. This could lead to a crash of the target system, thereby causing a denial of service (DoS) attack. It is generally recommended to keep your kernel up-to-date to minimize the risk of exploitation by potential attackers.

Here's the code snippet that implements the mentioned fix in the Linux kernel

static void discover_upi_topology(struct pci_dev *pdev)
{
    ...
    logical_socket_id = /* Get the logical socket id here */;
    nid = min(intel_uncore_pmu_num_boxes(us_pdev),
              logical_socket_id);
    ...
    upi = &type->topology[nid][idx];
    ...
}

Conditions:
   ...
}

This change ensures that the 'nid' variable is set correctly, preventing the out-of-bound access and NULL pointer dereference.

Original References and Links

1. The Linux kernel source repository on Github, where the mentioned fix was implemented: Linux Kernel Source Repository

2. The official Linux kernel mailing list announcement related to this vulnerability fix: Linux Kernel Mailing List

3. The official CVE database entry for this vulnerability: CVE-2023-52450

Conclusion

The Linux kernel developers have resolved a security vulnerability (CVE-2023-52450) in the kernel's perf/x86/intel/uncore subsystem that was caused by a NULL pointer dereference issue. By updating the kernel to get the logical socket id instead of the physical id in the discover_upi_topology() function, they have mitigated the risk of an attacker potentially exploiting this vulnerability. As always, it is advisable to keep your Linux kernel up-to-date to ensure the most secure and stable system performance.

Timeline

Published on: 02/22/2024 17:15:08 UTC
Last modified on: 03/18/2024 18:34:16 UTC