On 9/8/22 1:36 PM, 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. Ok. Thanks for clarifying it. I will fix it in next version. -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
