linux-kernel - Re: [PATCH] SVM: nSVM: fix resource leak on error path

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Date:   Tue, 15 Sep 2020 12:07:25 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Alex Dewar <alex.dewar90@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] SVM: nSVM: fix resource leak on error path

On Mon, 2020-09-14 at 20:45 +0100, Alex Dewar wrote:
> In svm_set_nested_state(), if nested_svm_vmrun_msrpm() returns false,
> then variables save and ctl will leak. Fix this.
> 
> Fixes: 772b81bb2f9b ("SVM: nSVM: setup nested msr permission bitmap on nested state load")
> Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
> ---
>  arch/x86/kvm/svm/nested.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 598a769f1961..85f572cbabe4 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1148,7 +1148,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
>  	nested_prepare_vmcb_control(svm);
>  
>  	if (!nested_svm_vmrun_msrpm(svm))
> -		return -EINVAL;
> +		goto out_free;	/* ret == -EINVAL */
>  
>  out_set_gif:
>  	svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));

I think that this patch is based on unmerged patch, since I don't see
any memory allocation in nested_svm_vmrun_msrpm, nor out_free label.
in nether kvm/master, kvm/queue nor in upstream/master

If I recall correctly that would be something about allocating ctrl/save
dynamically rather than on stack.

Best regards,
	Maxim Levitsky