On Mon, Mar 01, 2021 at 07:26:00PM +0800, Wang Qing wrote: > The copy_to_user() function returns the number of bytes remaining to be > copied, but we want to return -EFAULT if the copy doesn't complete. ... which is done by the only caller. if (set_fd_set(n, inp, fds.res_in) || set_fd_set(n, outp, fds.res_out) || set_fd_set(n, exp, fds.res_ex)) ret = -EFAULT;