Re: [bug report] SVM: nSVM: setup nested msr permission bitmap on nested state load

[Maxim Levitsky <mlevitsk@redhat.com>]

On Wed, 2020-09-23 at 16:44 +0300, Dan Carpenter wrote:
> Hello Maxim Levitsky,
> 
> The patch 772b81bb2f9b: "SVM: nSVM: setup nested msr permission
> bitmap on nested state load" from Aug 27, 2020, leads to the
> following static checker warning:
> 
> 	arch/x86/kvm/svm/nested.c:1161 svm_set_nested_state()
> 	warn: 'ctl' not released on lines: 1152.
> 
> arch/x86/kvm/svm/nested.c
>   1135          if (!(save->cr0 & X86_CR0_PG))
>   1136                  goto out_free;
>   1137  
>   1138          /*
>   1139           * All checks done, we can enter guest mode.  L1 control fields
>   1140           * come from the nested save state.  Guest state is already
>   1141           * in the registers, the save area of the nested state instead
>   1142           * contains saved L1 state.
>   1143           */
>   1144          copy_vmcb_control_area(&hsave->control, &svm->vmcb->control);
>   1145          hsave->save = *save;
>   1146  
>   1147          svm->nested.vmcb = kvm_state->hdr.svm.vmcb_pa;
>   1148          load_nested_vmcb_control(svm, ctl);
>   1149          nested_prepare_vmcb_control(svm);
>   1150  
>   1151          if (!nested_svm_vmrun_msrpm(svm))
>   1152                  return -EINVAL;
> 
> goto out_free?
> 
>   1153  
>   1154          svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
>   1155  
>   1156          ret = 0;
>   1157  out_free:
>   1158          kfree(save);
>   1159          kfree(ctl);
>   1160  
>   1161          return ret;
>   1162  }
> 
> regards,
> dan carpenter
> 
Which kernel tree is this? 

This again seems to be the result of other commit
that made save, ctl to be dynamically allocated. I based my patch on the version
that allocates both on the stack so no freeing is needed.

As far as I know from a check I did about week ago, none of branches on 
git://git.kernel.org/pub/scm/virt/kvm/kvm.git had that patch (that made save/ctr
be allocated dynamically).

Best regards,
	Maxim Levitsky