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

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Message-Id: <20210315041844.64915-4-gshan@redhat.com>
Date:   Mon, 15 Mar 2021 12:18:43 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-kernel@...r.kernel.org, maz@...nel.org, will@...nel.org,
        alexandru.elisei@....com, shan.gavin@...il.com
Subject: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

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;
 
-- 
2.23.0