linux-kernel - Re: [PATCH] KVM: SVM: Fix potential memory leak in svm_cpu

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Date:   Thu, 02 Jan 2020 14:30:50 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     liran.alon@...cle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, sean.j.christopherson@...el.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Subject: Re: [PATCH] KVM: SVM: Fix potential memory leak in svm_cpu_init()

linmiaohe <linmiaohe@...wei.com> writes:

> From: Miaohe Lin <linmiaohe@...wei.com>
>
> When kmalloc memory for sd->sev_vmcbs failed, we forget to free the page
> held by sd->save_area.
>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  arch/x86/kvm/svm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 8f1b715dfde8..89eb382e8580 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1012,7 +1012,7 @@ static int svm_cpu_init(int cpu)
>  	r = -ENOMEM;
>  	sd->save_area = alloc_page(GFP_KERNEL);
>  	if (!sd->save_area)
> -		goto err_1;
> +		goto free_cpu_data;
>  
>  	if (svm_sev_enabled()) {
>  		r = -ENOMEM;

Not your fault but this assignment to 'r' seem to be redundant: it is
already set to '-ENOMEM' above, but this is also not perfect as ... 

> @@ -1020,14 +1020,16 @@ static int svm_cpu_init(int cpu)
>  					      sizeof(void *),
>  					      GFP_KERNEL);
>  		if (!sd->sev_vmcbs)
> -			goto err_1;
> +			goto free_save_area;
>  	}
>  
>  	per_cpu(svm_data, cpu) = sd;
>  
>  	return 0;
>  
> -err_1:
> +free_save_area:
> +	__free_page(sd->save_area);
> +free_cpu_data:
>  	kfree(sd);
>  	return r;

... '-ENOMEM' is actually the only possible outcome here. In case you'll
be re-submitting, I'd suggest we drop 'r' entirely and just reture
-ENOMEM here.

Anyways, your patch seems to be correct, so:

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly