CVE-2024-50069 is a recently discovered and fixed vulnerability in the Linux kernel, specifically within the Apple pin control ("pinctrl") driver. This might sound like tech jargon, but the implications can be significant for devices using Apple's SOC (System on Chip) hardware running on Linux-based systems. In this post, we'll break down what went wrong, how it was fixed, and give you clear and exclusive insight into the mechanics, including code snippets and pointers on exploits.
What is the Vulnerability All About?
At its core, CVE-2024-50069 was caused by not properly checking the return value of the function devm_kasprintf(). This function is used within the Linux kernel for dynamic, managed memory allocation and string formatting. If this allocation fails, it returns NULL, which must be checked to prevent unexpected issues (like kernel crashes or information leaks).
Where Exactly?
The vulnerability lies inside the pinctrl-apple.c source file, which implements support for pin control on Apple’s ARM chips. Here, devm_kasprintf() is used to allocate and format device names, but the code failed to check if the memory allocation succeeded.
Why is this a Problem?
Whenever C code calls a function that might return NULL (none or zero), it should _always_ check the result before using it. Failing to do so can cause the kernel to dereference a NULL pointer, leading to serious issues like:
Potentially more severe kernel exploitation, though unlikely in this specific case due to context
This vulnerability was found by code review, meaning a developer carefully reading the code spotted the risk.
The Core Flaw — Code Snippet
Let’s look at a simplified version of the problematic code. Here’s what it looked like before the fix:
/* Vulnerable code */
state->chip.label = devm_kasprintf(dev, GFP_KERNEL, "%s-pinctrl", dev->of_node->name);
/* Oops: No check if state->chip.label is NULL! */
If devm_kasprintf() fails, state->chip.label will be NULL, and later code might misbehave, causing system instability.
The fixed code now checks the return value
/* Fixed code */
state->chip.label = devm_kasprintf(dev, GFP_KERNEL, "%s-pinctrl", dev->of_node->name);
if (!state->chip.label)
return -ENOMEM; // Return an "out of memory" error, gracefully
Can This Be Exploited?
In real-world exploitation terms: this bug on its own probably won't lead to "remote code execution" or privilege escalation, because it's in a relatively isolated (hardware-initializing) part of the kernel. However, it means the kernel could die unexpectedly if a memory error happened at just the wrong time, potentially causing denial of service or hardware weirdness.
Forcing kernel memory pressure so devm_kasprintf() fails
- Triggering the affected code path (by probing the pin control hardware or manipulating device tree nodes)
But since the window of exploitation is narrow and it only leads to a crash, it's not as critical as other kernel bugs—but it's still serious engineering hygiene.
How Was It Fixed?
The Linux kernel maintainers fixed this by adding the simple check above. This patch was included in newer stable releases.
Reference:
- Linux kernel commit fixing CVE-2024-50069
- Kernel bug tracker discussion
Protection & Mitigation
- Update your kernel! This fix is already in newer mainline Linux versions and backported to LTS versions.
If you maintain custom kernel code, check every function call that might return NULL!
- For embedded/IoT vendors: Validate device trees and memory reliability.
Conclusion
CVE-2024-50069 is a neat example of how small oversights in kernel C code, like not checking a potentially NULL return, can snowball into real bugs. Thanks to careful code review and the responsive open-source community, these issues can be squashed quickly. It’s yet another reminder: always check your return values, and stay patched!
References
- Upstream kernel fix
- CVE Details Entry (when available)
- Linux kernel documentation: Managed Device Resources
Timeline
Published on: 10/29/2024 01:15:04 UTC
Last modified on: 10/30/2024 16:58:19 UTC