A memory leak vulnerability has been discovered and resolved in the Linux kernel, specifically in the media subsystem's "v4l2-tpg" component (Video4Linux 2 Test Pattern Generator). Vulnerability CVE-2024-27078 relates to the improper allocation and deallocation of resources in certain error-handling paths, potentially causing memory leaks that may lead to system performance degradation or crashes. This post will provide an overview of the vulnerability, including affected versions, potential exploitation methods, and details on the patch that fixes this issue. Finally, some code snippets and links to original references will be included for a better understanding of the exploit and fix.

Affected Versions

The vulnerability affects Linux kernel versions 5.x before the patch "media: v4l2-tpg: fix some memleaks in tpg_alloc" is applied. If you are using a kernel version in this range, it is recommended to update to the latest release or apply the specific patch for this vulnerability.

Exploit Details

The vulnerability is located in the "tpg_alloc" function, which is responsible for allocating resources for the Test Pattern Generator in the kernel media subsystem. Due to improper resource allocation and deallocation in certain error-handling paths, memory leaks can occur. These leaks could cause the system to allocate an excessive amount of memory, leading to system degradation and potentially causing a crash.

Since the Test Pattern Generator is a user-facing component, an attacker must be able to run their code on the target system to exploit this vulnerability. In most scenarios, this would require an attacker to already have compromised the system or have the ability to execute arbitrary code through another vulnerability.

Fix Details

The patch for this issue, titled "media: v4l2-tpg: fix some memleaks in tpg_alloc," resolves the memory leak by ensuring that resources are properly deallocated in each error-handling path in the "tpg_alloc" function.

The following code snippet demonstrates a simplified version of the erroneous resource allocation, which can lead to memory leaks:

for (i = ; i < TPG_MAX_BUFFERS; i++) {
    tpg->sd.obj[k] = obj_alloc(obj, tpg->frequency);
    if (IS_ERR(tpg->sd.obj[k])) {
        err = PTR_ERR(tpg->sd.obj[k]);
        goto error;
    }
}

In this block of code, the "for" loop iterates through each buffer object and attempts to allocate resources using the "obj_alloc" function. However, if the "obj_alloc" function returns an error (indicated by the "IS_ERR" macro), the loop jumps immediately to the "error" label, without releasing the previously allocated resources.

The fix for this issue properly deallocates resources by simplifying the error-handling logic in the "tpg_alloc" function, ensuring that resources are released for all error cases to prevent memory leaks. The corrected version can be seen in the following code snippet:

for (i = ; i < TPG_MAX_BUFFERS; i++) {
    tpg->sd.obj[k] = obj_alloc(obj, tpg->frequency);
    if (IS_ERR(tpg->sd.obj[k])) {
        err = PTR_ERR(tpg->sd.obj[k]);
        tpg->sd.obj[k] = NULL;
        tpg_free(obj);
        return err;
    }
}

In this corrected version, any previously allocated resources are properly released by calling the "tpg_free" function before returning the error code.

Original References

- Linux source code repository with the patch applied

- v4l2-tpg: Test Pattern Generator documentation

Conclusion

CVE-2024-27078 is a recently patched memory leak vulnerability in the Linux kernel, which could potentially cause system performance degradation or crashes. The vulnerability has been fixed in the latest kernel releases, and users are advised to update their systems to ensure protection against potential exploitation.

Timeline

Published on: 05/01/2024 13:15:51 UTC
Last modified on: 12/23/2024 14:34:14 UTC