From: Tiezhu Yang > Sent: 11 December 2021 03:33 > > v2: > -- add copy_to_user_or_kernel() in lib/usercopy.c > -- define userbuf as bool type Instead of having a flag to indicate whether the buffer is user or kernel, would it be better to have two separate buffer pointers. One for a user space buffer, the other for a kernel space buffer. Exactly one of the buffers should always be NULL. That way the flag is never incorrectly set. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)