On Thu, Sep 08, 2022 at 01:36:00PM -0700, Dave Hansen wrote: > On 9/8/22 12:07, Sathyanarayanan Kuppuswamy wrote: > > On 9/7/22 10:31 PM, Greg Kroah-Hartman wrote: > >> On Wed, Sep 07, 2022 at 05:27:20PM -0700, Kuppuswamy Sathyanarayanan wrote: > >>> + /* > >>> + * Per TDX Module 1.0 specification, section titled > >>> + * "TDG.MR.REPORT", REPORTDATA length is fixed as > >>> + * TDX_REPORTDATA_LEN, TDREPORT length is fixed as > >>> + * TDX_REPORT_LEN, and TDREPORT subtype is fixed as > >>> + * 0. Also check for valid user pointers. > >>> + */ > >>> + if (!req.reportdata || !req.tdreport || req.subtype || > >>> + req.rpd_len != TDX_REPORTDATA_LEN || > >>> + req.tdr_len != TDX_REPORT_LEN) > >>> + return -EINVAL; > >> You never verify that your reserved[7] fields are actually set to 0, > >> which means you can never use them in the future :( > > Currently, we don't use those fields in our code. Why do we have to > > make sure they are set to zero? > > Yes. > > > Can't we add checks when we really use them in future? > > No. > > This has been a hard learned lesson both by people writing software and > designing hardware interfaces: if you _let_ folks pass garbage you have > to _keep_ letting them pass garbage forever. It becomes part of the ABI. > > I'm sorry you missed the memo on this one. But, this is one million > percent a best practice across the industry. Please do it. And it's documented in the Documentation/ directory as a requirement to do as well, the memo shouldn't have been missed :(
