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[PATCH 0/3] kvm: arm/arm64: Fixes for use after free problems

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  [PATCH 0/3]  kvm: arm/arm64: Fixes for use after free problems Suzuki K Poulose <suzuki.poulose@arm.com> - 2017-03-14 16:00 +0100
    [PATCH 2/3] kvm: arm/arm64: Take mmap_sem in kvm_arch_prepare_memory_region Suzuki K Poulose <suzuki.poulose@arm.com> - 2017-03-14 16:00 +0100
      Re: [PATCH 2/3] kvm: arm/arm64: Take mmap_sem in  kvm_arch_prepare_memory_region Christoffer Dall <cdall@linaro.org> - 2017-03-15 12:10 +0100

#1600536 — [PATCH 0/3] kvm: arm/arm64: Fixes for use after free problems

This series contains potential fixes for problems reported by [0] & [1].

[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-March/492944.html
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-March/492943.html


Marc Zyngier (2):
  kvm: arm/arm64: Take mmap_sem in stage2_unmap_vm
  kvm: arm/arm64: Take mmap_sem in kvm_arch_prepare_memory_region

Suzuki K Poulose (1):
  kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd

 arch/arm/kvm/mmu.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

-- 
2.7.4

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#1600542 — [PATCH 2/3] kvm: arm/arm64: Take mmap_sem in kvm_arch_prepare_memory_region

From: Marc Zyngier <marc.zyngier@arm.com>

We don't hold the mmap_sem while searching for VMAs (via find_vma), in
kvm_arch_prepare_memory_region, which can end up in expected failures.

Fixes: commit 8eef91239e57 ("arm/arm64: KVM: map MMIO regions at creation time")
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Eric Auger <eric.auger@rehat.com>
Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[ Handle dirty page logging failure case ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 arch/arm/kvm/mmu.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index f2e2e0c..13b9c1f 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1803,6 +1803,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	    (KVM_PHYS_SIZE >> PAGE_SHIFT))
 		return -EFAULT;
 
+	down_read(&current->mm->mmap_sem);
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
 	 * between them, so iterate over all of them to find out if we can map
@@ -1846,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 			pa += vm_start - vma->vm_start;
 
 			/* IO region dirty page logging not allowed */
-			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
-				return -EINVAL;
+			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+				ret = -EINVAL;
+				goto out;
+			}
 
 			ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
 						    vm_end - vm_start,
@@ -1859,7 +1862,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)
@@ -1867,6 +1870,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 
-- 
2.7.4

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#1601287 — Re: [PATCH 2/3] kvm: arm/arm64: Take mmap_sem in kvm_arch_prepare_memory_region

On Tue, Mar 14, 2017 at 02:52:33PM +0000, Suzuki K Poulose wrote:
> From: Marc Zyngier <marc.zyngier@arm.com>
> 
> We don't hold the mmap_sem while searching for VMAs (via find_vma), in
> kvm_arch_prepare_memory_region, which can end up in expected failures.
> 
> Fixes: commit 8eef91239e57 ("arm/arm64: KVM: map MMIO regions at creation time")
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> Cc: Eric Auger <eric.auger@rehat.com>
> Cc: stable@vger.kernel.org # v3.18+
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> [ Handle dirty page logging failure case ]
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

> ---
>  arch/arm/kvm/mmu.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index f2e2e0c..13b9c1f 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -1803,6 +1803,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	    (KVM_PHYS_SIZE >> PAGE_SHIFT))
>  		return -EFAULT;
>  
> +	down_read(&current->mm->mmap_sem);
>  	/*
>  	 * A memory region could potentially cover multiple VMAs, and any holes
>  	 * between them, so iterate over all of them to find out if we can map
> @@ -1846,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  			pa += vm_start - vma->vm_start;
>  
>  			/* IO region dirty page logging not allowed */
> -			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
> -				return -EINVAL;
> +			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> +				ret = -EINVAL;
> +				goto out;
> +			}
>  
>  			ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>  						    vm_end - vm_start,
> @@ -1859,7 +1862,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	} while (hva < reg_end);
>  
>  	if (change == KVM_MR_FLAGS_ONLY)
> -		return ret;
> +		goto out;
>  
>  	spin_lock(&kvm->mmu_lock);
>  	if (ret)
> @@ -1867,6 +1870,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	else
>  		stage2_flush_memslot(kvm, memslot);
>  	spin_unlock(&kvm->mmu_lock);
> +out:
> +	up_read(&current->mm->mmap_sem);
>  	return ret;
>  }
>  
> -- 
> 2.7.4
> 

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