CVE-2023-52809 - Fixing NULL Pointer Dereference in the Linux Kernel's SCSI Subsystem

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In the Linux kernel, an important vulnerability has been resolved. This vulnerability affected the SCSI protocol subsystem, in a function called fc_lport_ptp_setup(). The issue resided in a potential NULL pointer dereference that could crash the Linux kernel. This article will describe the details of the CVE-2023-52809 vulnerability, the fix that has been implemented, and links to the original sources for a deeper understanding.

The Vulnerability

The vulnerability affects the SCSI subsystem in the Linux kernel, particularly the libfc module. Libfc is responsible for implementing Fibre Channel Protocol (FCP) over Ethernet in the kernel. The function fc_lport_ptp_setup() sets up point-to-point (PtP) connections in the FCP. This function was not checking the return value of another function fc_rport_create() properly, which could lead to a situation where the kernel tries to access data from a NULL pointer. This situation would cause a kernel crash and would negatively affect the stability and reliability of the system using the kernel.

The Fix

The fix for the CVE-2023-52809 vulnerability addresses the NULL pointer dereference issue by adding checks for the return value of the fc_rport_create() function. If the fc_rport_create() function returns NULL, the kernel should not attempt to access the memory location pointed by the pointer. The fix adds proper error handling in the fc_lport_ptp_setup() function to ensure that the kernel can handle the situation correctly.

Here is a code snippet from the patch that demonstrates the fix in action

struct fc_rport_priv *rdata;

rdata = fc_rport_create(lport, rport_id);
if (!rdata) {
    /* Properly handle the error */
    return -ENOMEM;
}

This code snippet shows the addition of the check for the return value of the fc_rport_create() function, and a proper error handling using the error code -ENOMEM.

In addition to the fix itself, the patch also includes reporting and logging functions that notify the user in the event of a failure. This ensures that proper steps can be taken to handle and diagnose any issues that arise from a failure in the fc_rport_create() function.

For more information on this vulnerability, look into the following resources

1. Linux Kernel Mailing List (LKML) Patch - This is the original patch that introduced the fix, submitted by the author Hareesh.

2. Linux Security Vulnerability Database - A reference to the CVE-2023-52809 and detailed information can be found in this database.

3. Linux Kernel Git Repository - You can examine all the commits, including the fix, in the official Linux kernel git repository.

Exploit Details

While no explicit exploit has been reported or documented for the CVE-2023-52809 vulnerability, it is essential to address this potential issue to maintain the integrity and reliability of systems using the affected Linux kernel with SCSI support. The exploitation of the bug could lead to kernel crashes and potentially open the door for further exploitation. The potential for Denial-of-Service (DoS) attacks on systems with vulnerable kernels underlines the importance of patching and keeping the kernel up to date.

Conclusion

The CVE-2023-52809 vulnerability in the SCSI subsystem of the Linux kernel has now been addressed through appropriate NULL pointer checking. The new error handling mechanisms will ensure that the kernel doesn't crash in the event of a NULL return by the fc_rport_create() function. It is highly recommended to update your Linux kernel to the latest version, as this will protect your system from this vulnerability and other known issues.

Timeline

Published on: 05/21/2024 16:15:19 UTC
Last modified on: 05/24/2024 01:14:23 UTC