From: Matthew Wilcox > Sent: 12 December 2021 11:48 > > On Sat, Dec 11, 2021 at 05:53:46PM +0000, David Laight wrote: > > 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. > > No. You should be using an iov_iter instead. See > https://lore.kernel.org/all/Ya4bdB0UBJCZhUSo@xxxxxxxxxxxxxxxxxxxx/ > for a start on this. iov_iter gets horribly expensive... David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
