Re: FAILED: patch "[PATCH] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read" failed to apply to 4.19-stable tree

[Marc Zyngier <maz@kernel.org>]

On Wed, 12 May 2021 11:46:23 +0100,
<gregkh@linuxfoundation.org> wrote:
> 
> 
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> From 94ac0835391efc1a30feda6fc908913ec012951e Mon Sep 17 00:00:00 2001
> From: Eric Auger <eric.auger@redhat.com>
> Date: Mon, 12 Apr 2021 17:00:34 +0200
> Subject: [PATCH] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read
> 
> 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@vger.kernel.org> # v4.18+
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Reported-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> index 2f66cf247282..7740995de982 100644
> --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
> +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> @@ -87,8 +87,8 @@ 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

Eric, any chance you could look at a potential backport of this patch
to both 4.19 and 5.4?

Thanks a lot,

	M.

-- 
Without deviation from the norm, progress is not possible.