Linux Kernel x86-64 Function Name Change for Improved Clarity

A naming issue in the Linux kernel's memory copy function '__copy_user_nocache()' has been addressed. This function, used in the x86-64 architecture, falsely claimed to provide a non-cached user copy. In reality, it was neither non-cached nor a proper user copy. The function has been renamed to 'copy_to_nontemporal' to better reflect its purpose. The update includes a revision of the function's prototype for clarity and correctness. The renamed function is now utilized in the NTB (Non-Transparent Bridge) code, replacing the previous, misused user copy version.

Impact

The impact of this change is primarily on code clarity and correctness. By renaming the function and updating its usage, potential misunderstandings about its functionality are mitigated, leading to more accurate and reliable code execution.

Reproduction

The vulnerability can be reproduced by using the misnamed '__copy_user_nocache()' function in a driver or application context where its incorrect behavior can be demonstrated, such as in certain Infiniband drivers or the NTB transport layer. This will involve copying data to a non-temporal destination without proper exception handling, which can be done by bypassing the usual user space access protocols.

Remediation

The function has been renamed and its usage corrected in the Linux kernel stable tree. Users should update to the latest version of the kernel where this change has been implemented.