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.
