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

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Date:   Mon, 16 Nov 2020 22:57:26 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <kvmarm@...ts.cs.columbia.edu>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <eric.auger@...hat.com>,
        <james.morse@....com>, <julien.thierry.kdev@...il.com>,
        <suzuki.poulose@....com>, <wanghaibin.wang@...wei.com>,
        Keqian Zhu <zhukeqian1@...wei.com>
Subject: Re: [PATCH 1/2] KVM: arm64: vgic: Forbid invalid userspace
 Redistributor accesses

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