linux-kernel - Re: [PATCH 1/2] KVM: SVM: Fix uninitialized variable bug

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Message-ID: <ZrrcR-kJ8hP6afWb@google.com>
Date: Mon, 12 Aug 2024 21:08:39 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: error27@...il.com, Paolo Bonzini <pbonzini@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Ashish Kalra <ashish.kalra@....com>, 
	Brijesh Singh <brijesh.singh@....com>, Michael Roth <michael.roth@....com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: SVM: Fix uninitialized variable bug

On Wed, Jun 12, 2024, Dan Carpenter wrote:
> If snp_lookup_rmpentry() fails then "assigned" is printed in the error
> message but it was never initialized.  Initialize it to false.
> 
> Fixes: dee5a47cc7a4 ("KVM: SEV: Add KVM_SEV_SNP_LAUNCH_UPDATE command")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> The compiler is generally already zeroing stack variables so this doesn't cost
> anything.
> 
>  arch/x86/kvm/svm/sev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 43a450fb01fd..70d8d213d401 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2199,7 +2199,7 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn_start, kvm_pfn_t pf
>  
>  	for (gfn = gfn_start, i = 0; gfn < gfn_start + npages; gfn++, i++) {
>  		struct sev_data_snp_launch_update fw_args = {0};
> -		bool assigned;
> +		bool assigned = false;

I would rather delete all the printks, or if people really like the printks, at
least provide some helpers to dedup the code.  E.g. sev_gmem_prepare() has more
or less the exact same behavior, but doesn't have the same flaw.

>  		int level;
>  
>  		if (!kvm_mem_is_private(kvm, gfn)) {
> -- 
> 2.43.0
>