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

[Ben Widawsky]

On 21-02-16 18:12:05, Al Viro wrote:
> 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.

mea culpa. In fact it was previously memdup_user and Dan suggested I switch to
vmemdup_user.
https://lore.kernel.org/linux-cxl/CAPcyv4j+ixVgEo5q2OhV4kdkBZbnohZj3KDovReQJjPBsREugw@xxxxxxxxxxxxxx/


Will fix for the next version.

Thanks.