linux-kernel - Re: [PATCH v2 03/25] x86/virt/tdx: Read essential global metadata for KVM

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Message-ID: <11479069-6f1d-42b8-81b6-376603aea76f@intel.com>
Date: Fri, 6 Dec 2024 08:24:34 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Huang, Kai" <kai.huang@...el.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>,
 "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "Chatre, Reinette" <reinette.chatre@...el.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "Zhao, Yan Y" <yan.y.zhao@...el.com>,
 "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
 "tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>
Subject: Re: [PATCH v2 03/25] x86/virt/tdx: Read essential global metadata for
 KVM

On 12/6/24 08:13, Huang, Kai wrote:
> It is not safe. We need to check
> 
>       sysinfo_td_conf->num_cpuid_config <= 32.
> 
> If the TDX module version is not matched with the json file that was
> used to generate the tdx_global_metadata.h, the num_cpuid_config
> reported by the actual TDX module might exceed 32 which causes
> out-of-bound array access.

The JSON *IS* the ABI description. It can't change between versions of
the TDX module. It can only be extended. The "32" is not in the spec
because the spec refers to the JSON!