linux-kernel - Re: [PATCH] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE

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Message-ID: <f8e6aab9-651c-9ef1-2621-6d61374704cc@redhat.com>
Date:   Mon, 21 Jun 2021 14:21:48 +0200
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, stable@...r.kernel.org, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read

Hi,

On 6/21/21 2:18 PM, Eric Auger wrote:
> When reading the base address of the a REDIST region
> through KVM_VGIC_V3_ADDR_TYPE_REDIST we expect the
> redistributor region list to be populated with a single
> element.
>
> However list_first_entry() expects the list to be non empty.
> Instead we should use list_first_entry_or_null which effectively
> returns NULL if the list is empty.
>
> Fixes: dbd9733ab674 ("KVM: arm/arm64: Replace the single rdist region by a list")
> Cc: <Stable@...r.kernel.org> # v4.19
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> Reported-by: Gavin Shan <gshan@...hat.com>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com

Maybe I should I prefixed the patch with [stable-4.19]. This is already
on master and in various stable but did not apply on 4.19

Thanks

Eric
> ---
>  virt/kvm/arm/vgic/vgic-kvm-device.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
> index 6ada2432e37c..71d92096776e 100644
> --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
> +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
> @@ -95,8 +95,8 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write)
>  			r = vgic_v3_set_redist_base(kvm, 0, *addr, 0);
>  			goto out;
>  		}
> -		rdreg = list_first_entry(&vgic->rd_regions,
> -					 struct vgic_redist_region, list);
> +		rdreg = list_first_entry_or_null(&vgic->rd_regions,
> +						 struct vgic_redist_region, list);
>  		if (!rdreg)
>  			addr_ptr = &undef_value;
>  		else