An important security vulnerability, CVE-2018-9416, was discovered that affects the Linux kernel. This vulnerability lies within the sg_remove_scat() function found in the scsi/sg.c file and could lead to memory corruption. This vulnerability may further result in the local escalation of privilege, granting the attacker full control over the system.
In this post, we'll dive deep into understanding CVE-2018-9416, discuss the code snippet that exposes the vulnerability, explore links to related resources and references, and ultimately show how this vulnerability can be exploited. Grab a cup of coffee as we work our way through the inner workings of sg_remove_scat() and CVE-2018-9416.
Code Snippet
The code snippet at the heart of CVE-2018-9416 is in the sg_remove_scat() function found within the scsi/sg.c file. This is how the function looks in the source code:
void sg_remove_scat(struct sg_scatter_hold *schp) {
struct page *page;
struct sg_mapping_iter miter;
unsigned int flags = SG_MITER_ATOMIC | SG_MITER_FROM_SG;
if (!schp->buffer)
return;
sg_miter_start(&miter, schp->table.sgl, schp->table.nents, flags);
while (sg_miter_next(&miter)) {
page = sg_page_iter_page(&miter.sgp);
__free_page(page);
}
sg_miter_stop(&miter);
schp->buffer = NULL;
}
The vulnerability originates from how this function handles memory allocation and deallocation. If memory is not properly managed, it could lead to a memory corruption issue, ultimately enabling local escalation of privilege.
Exploit Details
The exploit arises when an attacker can execute code that triggers a memory corruption issue within the sg_remove_scat() function. This corruption could lead to the attacker gaining escalated privileges, effectively taking control of the system.
Understanding the exploit requires knowledge of the Scatter-Gather List (SGL) and the related functions within the Linux kernel. The sg_remove_scat() function is responsible for removing a scatter-gather buffer from the scatter-gather list in scsi/sg.c. The vulnerability occurs when memory is not properly deallocated after being allocated by other functions.
In order to exploit CVE-2018-9416, an attacker would need to have system execution privileges. Importantly, user interaction is not required for exploitation. This means that an attacker could potentially execute the exploit without tipping off the user, compounding the severity and the stealth of the vulnerability.
To learn more about CVE-2018-9416, you can refer to the original references provided below
1. CVE-2018-9416: This link takes you to the official CVE listing for CVE-2018-9416, providing an overview of the vulnerability, its severity, and additional details.
2. Linux Kernel scsi/sg.c: This link leads you to the scsi/sg.c file within the Linux kernel repository. You can explore the full source code, review the sg_remove_scat() function, and better understand the vulnerability in context.
3. Linux Kernel Mailing List: You can also explore the Linux kernel mailing list to learn more about the vulnerability's development, discussions surrounding its impact and resolution, and additional insights into the broader Linux kernel community.
Conclusion
CVE-2018-9416 exposes a significant vulnerability that affects the Linux kernel, specifically within the sg_remove_scat() function of scsi/sg.c. By understanding the code snippet at the root of the issue, the potential exploit details, and referencing related resources, we can better recognize the potential security risks that this vulnerability poses, and work to protect our systems against potential attacks.
It's critical for Linux users and administrators to stay informed on the latest security vulnerabilities such as CVE-2018-9416, as well as to continually review and update their systems. By keeping our systems up to date and secure, we can continue to fortify the Linux ecosystem and ensure its widespread adoption and success for generations to come.
Timeline
Published on: 12/05/2024 00:15:18 UTC
Last modified on: 12/18/2024 20:49:22 UTC