linux-kernel - Re: [PATCH v7 15/15] KVM: s390: fix possible null pointer dereference in pending

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Message-Id: <a40905b7-b2f0-22f4-348f-40a165681d08@linux.ibm.com>
Date:   Fri, 1 Feb 2019 10:36:10 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Michael Mueller <mimu@...ux.ibm.com>,
        KVM Mailing List <kvm@...r.kernel.org>
Cc:     Linux-S390 Mailing List <linux-s390@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>
Subject: Re: [PATCH v7 15/15] KVM: s390: fix possible null pointer dereference
 in pending_irqs()

On 31/01/2019 09:52, Michael Mueller wrote:
> Assure a GISA is in use before accessing the IPM to avoid a
> null pointer dereference issue.
> 
> Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
> Reported-by: Halil Pasic <pasic@...ux.ibm.com>
> ---
>   arch/s390/kvm/interrupt.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index d322400ca587..660ec87b6e60 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -329,9 +329,13 @@ static inline unsigned long pending_irqs_no_gisa(struct kvm_vcpu *vcpu)
>   
>   static inline unsigned long pending_irqs(struct kvm_vcpu *vcpu)
>   {
> -	return pending_irqs_no_gisa(vcpu) |
> -		gisa_get_ipm(vcpu->kvm->arch.gisa_int.origin) <<
> -			IRQ_PEND_IO_ISC_7;
> +	struct kvm_s390_gisa_interrupt *gi = &vcpu->kvm->arch.gisa_int;
> +	unsigned long pending_mask;
> +
> +	pending_mask = pending_irqs_no_gisa(vcpu);
> +	if (gi->origin)
> +		pending_mask |= gisa_get_ipm(gi->origin) << IRQ_PEND_IO_ISC_7;
> +	return pending_mask;
>   }
>   
>   static inline int isc_to_irq_type(unsigned long isc)
> 
Reviewed-by: Pierre Morel<pmorel@...ux.ibm.com>


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany