linux-kernel - Re: [PATCH v10 021/108] KVM: TDX: initialize VM with TDX specific parameters

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Date:   Thu, 17 Nov 2022 09:51:25 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "Wang, Lei" <lei4.wang@...el.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v10 021/108] KVM: TDX: initialize VM with TDX specific
 parameters

On Wed, Nov 16, 2022 at 01:34:46PM +0800,
"Wang, Lei" <lei4.wang@...el.com> wrote:

> > @@ -431,50 +633,65 @@ int tdx_vm_init(struct kvm *kvm)
> >  	return ret;
> >  }
> >  
> > -int tdx_dev_ioctl(void __user *argp)
> > +static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
> >  {
> > -	struct kvm_tdx_capabilities __user *user_caps;
> > -	struct kvm_tdx_capabilities caps;
> > -	struct kvm_tdx_cmd cmd;
> > +	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> > +	struct kvm_tdx_init_vm *init_vm = NULL;
> > +	struct td_params *td_params = NULL;
> > +	void *entries_end;
> > +	int ret;
> >  
> > -	BUILD_BUG_ON(sizeof(struct kvm_tdx_cpuid_config) !=
> > -		     sizeof(struct tdx_cpuid_config));
> > +	BUILD_BUG_ON(sizeof(*init_vm) != 16 * 1024);
> > +	BUILD_BUG_ON((sizeof(*init_vm) - offsetof(typeof(*init_vm), entries)) /
> > +		     sizeof(init_vm->entries[0]) < KVM_MAX_CPUID_ENTRIES);
> > +	BUILD_BUG_ON(sizeof(struct td_params) != 1024);
> >  
> > -	if (copy_from_user(&cmd, argp, sizeof(cmd)))
> > -		return -EFAULT;
> > -	if (cmd.flags || cmd.error || cmd.unused)
> > +	if (is_td_initialized(kvm))
> >  		return -EINVAL;
> > -	/*
> > -	 * Currently only KVM_TDX_CAPABILITIES is defined for system-scoped
> > -	 * mem_enc_ioctl().
> > -	 */
> > -	if (cmd.id != KVM_TDX_CAPABILITIES)
> > +
> > +	if (cmd->flags)
> >  		return -EINVAL;
> >  
> > -	user_caps = (void __user *)cmd.data;
> > -	if (copy_from_user(&caps, user_caps, sizeof(caps)))
> > -		return -EFAULT;
> > +	init_vm = kzalloc(sizeof(*init_vm), GFP_KERNEL);
> > +	if (copy_from_user(init_vm, (void __user *)cmd->data, sizeof(*init_vm))) {
> 
> Pointer 'init_vm' returned from call to function 'kzalloc' may be NULL and will
> be dereferenced at this line.
> 
> Maybe a NULL-check here is needed?

Yes, thank you for catching it.

Thanks,
-- 
Isaku Yamahata <isaku.yamahata@...il.com>