linux-kernel - Re: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

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Date:   Mon, 15 Mar 2021 20:46:30 +1100
From:   Gavin Shan <gshan@...hat.com>
To:     Keqian Zhu <zhukeqian1@...wei.com>, kvmarm@...ts.cs.columbia.edu
Cc:     maz@...nel.org, will@...nel.org, linux-kernel@...r.kernel.org,
        shan.gavin@...il.com
Subject: Re: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

Hi Keqian,

On 3/15/21 6:33 PM, Keqian Zhu wrote:
> FYI, this has been fixed by Marc in commit 262b003d059c.
> 

Yeah, I didn't check 5.12.rc3 code where the issue has been
fixed. So please ignore this one and sorry for the noise.

Thanks,
Gavin
  
> On 2021/3/15 12:18, Gavin Shan wrote:
>> The last (IPA) page can't be specified when a new memory slot is
>> added. The error -EFAULT is returned when the memory slot is added
>> with the following parameters for the VM, which has 40-bits IPA
>> limit. The host has 4KB base page size. It's not correct because
>> the last (IPA) page is still usable.
>>
>>     struct kvm_userspace_memory_region {
>>        __u32 slot;               /* 1            */
>>        __u32 flags;              /* 0            */
>>        __u64 guest_phys_addr;    /* 0xfffffff000 */
>>        __u64 memory_size;        /* 0x1000       */
>>        __u64 userspace_addr;
>>     };
>>
>> Signed-off-by: Gavin Shan <gshan@...hat.com>
>> ---
>>   arch/arm64/kvm/mmu.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 286b603ed0d3..a5a8ade9fde4 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -1313,7 +1313,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>   	 * Prevent userspace from creating a memory region outside of the IPA
>>   	 * space addressable by the KVM guest IPA space.
>>   	 */
>> -	if (memslot->base_gfn + memslot->npages >=
>> +	if (memslot->base_gfn + memslot->npages >
>>   	    (kvm_phys_size(kvm) >> PAGE_SHIFT))
>>   		return -EFAULT;
>>   
>>
>