CVE-2021-47003 - Linux Kernel Vulnerability: Fixing Null Dereference in dmaengine: idxd

In the Linux kernel, a vulnerability has been identified and resolved with CVE-2021-47003. This vulnerability is related to the dmaengine: idxd subsystem and can lead to a null pointer dereference, causing potential stability and security issues. This blog post will take a deep dive into the details of this vulnerability, its potential impact, and the steps taken to fix it.

Vulnerability Details

In the Linux kernel's dmaengine: idxd subsystem, there is a function called idxd_cmd_exec, which is responsible for managing data movement operations for hardware accelerators. This function takes a status pointer as one of its parameters.

However, there are instances where idxd_cmd_exec is called with a null status pointer, which can lead to a null pointer dereference. This issue arises due to the recent commit that has added an assignment to *status without first checking if the pointer is null.

This vulnerability was identified by Coverity static analysis tool under the bug category "Explicit null dereferenced".

Here is the relevant code snippet that demonstrates the issue

int idxd_cmd_exec(struct idxd_device *idxd, struct idxd_cmd *cmd, int *status)
{
        ...
        if (*status >= ) {
                ...
                *status = idxd->cmd_status.status;
        }
        ...
}

Fix Details

To fix this issue, a simple null check was added to the idxd_cmd_exec function before assigning a value to *status. This ensures that if the status pointer is null, the assignment statement is bypassed, and the function execution continues without causing a null pointer dereference error.

Here's the updated code snippet after applying the fix

int idxd_cmd_exec(struct idxd_device *idxd, struct idxd_cmd *cmd, int *status)
{
        ...
        if (status && *status >= ) {
                ...
                *status = idxd->cmd_status.status;
        }
        ...
}

As we can see, the proper null check has been implemented in the fixed code, ensuring the function operates as intended and doesn't cause null pointer dereference issues.

Original References and Acknowledgements

- A huge credit goes to the Linux Kernel developers and maintainers for their diligent work in identifying and fixing this crucial vulnerability.
- The original patch for this vulnerability can be found on the Linux Kernel mailing list: Linux Kernel Mailing List Patch
- The CVE details can be found on the official CVE website: CVE-2021-47003

In conclusion, the Linux kernel vulnerability CVE-2021-47003 related to the dmaengine: idxd subsystem has been addressed and fixed. The fix ensures that null pointer dereference issues are no longer a concern in the idxd_cmd_exec function. Users and developers relying on the Linux kernel should ensure they are using an updated version that includes this fix for a secure and stable system.

Timeline

Published on: 02/28/2024 09:15:38 UTC
Last modified on: 02/28/2024 14:06:45 UTC