dm ioctl: prevent potential spectre v1 gadget
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v4.19.238 by commit 7ae2c5b89da3cfaf856df880af27d3bb32a74b3d. For more details please see the references link.