linux-kernel - Re: [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm

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Date:   Mon, 3 May 2021 16:05:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Colin King <colin.king@...onical.com>,
        Sean Christopherson <seanjc@...gle.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>,
        Nathan Tempelman <natet@...gle.com>, kvm@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] KVM: x86: Fix potential fput on a null
 source_kvm_file

On 30/04/21 19:03, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The fget can potentially return null, so the fput on the error return
> path can cause a null pointer dereference. Fix this by checking for
> a null source_kvm_file before doing a fput.
> 
> Addresses-Coverity: ("Dereference null return")
> Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>   arch/x86/kvm/svm/sev.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 1356ee095cd5..8b11c711a0e4 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1764,7 +1764,8 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
>   e_source_unlock:
>   	mutex_unlock(&source_kvm->lock);
>   e_source_put:
> -	fput(source_kvm_file);
> +	if (source_kvm_file)
> +		fput(source_kvm_file);
>   	return ret;
>   }
>   
> 

Queued, thanks.

Paolo