Re: [PATCH 1/2] KVM: arm64: vgic: Forbid invalid userspace Redistributor accesses

From: Zenghui Yu <yuzenghui@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: <kvmarm@lists.cs.columbia.edu>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <eric.auger@redhat.com>,
	<james.morse@arm.com>, <julien.thierry.kdev@gmail.com>,
	<suzuki.poulose@arm.com>, <wanghaibin.wang@huawei.com>,
	Keqian Zhu <zhukeqian1@huawei.com>
Subject: Re: [PATCH 1/2] KVM: arm64: vgic: Forbid invalid userspace Redistributor accesses
Date: Mon, 16 Nov 2020 22:57:26 +0800	[thread overview]
Message-ID: <7e58200c-814e-3598-155a-9a7e6cc24374@huawei.com> (raw)
In-Reply-To: <cc45285fe491aff5c28a24f94c124508@kernel.org>

Hi Marc,

On 2020/11/16 22:10, Marc Zyngier wrote:
>> My take is that only if the "[Re]Distributor base address" is specified
>> in the system memory map, will the user-provided kvm_device_attr.offset
>> make sense. And we can then handle the access to the register which is
>> defined by "base address + offset".
> 
> I'd tend to agree, but it is just that this is a large change at -rc4.
> I'd rather have a quick fix for 5.10, and a more invasive change for 5.11,
> spanning all the possible vgic devices.

So you prefer fixing it by "return a value that doesn't have the Last
bit set" for v5.10? I'm ok with it and can send v2 for it.

Btw, looking again at the way we handle the user-reading of GICR_TYPER

	vgic_mmio_read_v3r_typer(vcpu, addr, len)

it seems that @addr is actually the *offset* of GICR_TYPER (0x0008) and
@addr is unlikely to be equal to last_rdist_typer, which is the *GPA* of
the last RD. Looks like the user-reading of GICR_TYPER.Last is always
broken?

Thanks,
Zenghui