CVE-2024-50005

In the Linux kernel, the following vulnerability has been resolved:

mac802154: Fix potential RCU dereference issue in mac802154_scan_worker

In the mac802154_scan_worker function, the scan_req->type field was accessed after the RCU read-side critical section was unlocked. According to RCU usage rules, this is illegal and can lead to unpredictable behavior, such as accessing memory that has been updated or causing use-after-free issues.

This possible bug was identified using a static analysis tool developed by myself, specifically designed to detect RCU-related issues.

To address this, the scan_req->type value is now stored in a local variable scan_req_type while still within the RCU read-side critical section. The scan_req_type is then used after the RCU lock is released, ensuring that the type value is safely accessed without violating RCU rules.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/540138377b22f601f06f55ebfa3ca171dcab471a
• https://git.kernel.org/stable/c/bff1709b3980bd7f80be6786f64cc9a9ee9e56da
• https://git.kernel.org/stable/c/d18f669461811dfe2915d5554ab2a9834f810013
• https://git.kernel.org/stable/c/e676e4ea76bbe7f1156d8c326b9b6753849481c2