Re: [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file

From: Paolo Bonzini <pbonzini@redhat.com>
To: Colin King <colin.king@canonical.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	Nathan Tempelman <natet@google.com>,
	kvm@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file
Date: Mon, 3 May 2021 16:05:21 +0200	[thread overview]
Message-ID: <9d28cde2-7aff-64bb-26f4-9909344676e5@redhat.com> (raw)
In-Reply-To: <20210430170303.131924-1-colin.king@canonical.com>

On 30/04/21 19:03, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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@canonical.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