Re: [PATCH v4 4/9] cxl/mem: Add basic IOCTL interface

On Mon, Feb 15, 2021 at 05:45:33PM -0800, Ben Widawsky wrote: > + if (cmd->info.size_in) { > + mbox_cmd.payload_in = kvzalloc(cmd->info.size_in, GFP_KERNEL); > + if (!mbox_cmd.payload_in) { > + rc = -ENOMEM; > + goto out; > + } > + > + if (copy_from_user(mbox_cmd.payload_in, > + u64_to_user_ptr(in_payload), > + cmd->info.size_in)) { > + rc = -EFAULT; > + goto out; > + } Umm... Do you need to open-code vmemdup_user()? The only difference is GFP_KERNEL allocation instead of GFP_USER one, and the latter is arguably saner here... Zeroing is definitely pointless - you either overwrite the entire buffer with copy_from_user(), or you fail and free the damn thing.