linux-kernel - Re: [PATCH 1/2] KVM: SVM: free sev_*asid

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Message-ID: <20230411224737.00001d67.zhi.wang.linux@gmail.com>
Date:   Tue, 11 Apr 2023 22:47:37 +0300
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Cc:     pbonzini@...hat.com, Sean Christopherson <seanjc@...gle.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: SVM: free sev_*asid_bitmap init if SEV init
 fails

On Tue,  4 Apr 2023 14:26:51 +0200
Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com> wrote:

> If misc_cg_set_capacity() fails for some reason then we have
> a memleak for sev_reclaim_asid_bitmap/sev_asid_bitmap. It's
> not a case right now, because misc_cg_set_capacity() just can't
> fail and check inside it is always successful.
> 
> But let's fix that for code consistency.
> 
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Stéphane Graber <stgraber@...ntu.com>
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
>  arch/x86/kvm/svm/sev.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c25aeb550cd9..a42536a0681a 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2213,8 +2213,13 @@ void __init sev_hardware_setup(void)
>  	}
>  
>  	sev_asid_count = max_sev_asid - min_sev_asid + 1;
> -	if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count))
> +	if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)) {
> +		bitmap_free(sev_reclaim_asid_bitmap);
> +		sev_reclaim_asid_bitmap = NULL;
> +		bitmap_free(sev_asid_bitmap);
> +		sev_asid_bitmap = NULL;
>  		goto out;
> +	}
>  
>  	pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
>  	sev_supported = true;

It would be nice that another case can also be fixed:

        sev_es_asid_count = min_sev_asid - 1;
        if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
                goto out; /* <----HERE */

Maybe it would be a good idea to factor out an common error handling path.