aio: fix mremap after fork null-deref
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 v4.19.273 by commit d8dca1bfe9adcae38b35add64977818c0c13dd22, it was introduced in version v3.19 by commit e4a0d3e720e7e508749c1439b5ba3aff56c92976. For more details please see the references link.