mac802154: Fix potential RCU dereference issue in mac802154_scan_worker

Vulnerability Description

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.

References

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