linux-kernel - [PATCH 3.19.y-ckt 33/86] arm: KVM: Fix incorrect device to IPA mapping

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Date:	Tue, 27 Oct 2015 14:29:33 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Marek Majtyka <marek.majtyka@...to.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 33/86] arm: KVM: Fix incorrect device to IPA mapping

3.19.8-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marek Majtyka <marek.majtyka@...to.com>

commit ca09f02f122b2ecb0f5ddfc5fd47b29ed657d4fd upstream.

A critical bug has been found in device memory stage1 translation for
VMs with more then 4GB of address space. Once vm_pgoff size is smaller
then pa (which is true for LPAE case, u32 and u64 respectively) some
more significant bits of pa may be lost as a shift operation is performed
on u32 and later cast onto u64.

Example: vm_pgoff(u32)=0x00210030, PAGE_SHIFT=12
        expected pa(u64):   0x0000002010030000
        produced pa(u64):   0x0000000010030000

The fix is to change the order of operations (casting first onto phys_addr_t
and then shifting).

Reviewed-by: Marc Zyngier <marc.zyngier@....com>
[maz: fixed changelog and patch formatting]
Signed-off-by: Marek Majtyka <marek.majtyka@...to.com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/arm/kvm/mmu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 9ec6dfe..0512ed4 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1439,8 +1439,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 		if (vma->vm_flags & VM_PFNMAP) {
 			gpa_t gpa = mem->guest_phys_addr +
 				    (vm_start - mem->userspace_addr);
-			phys_addr_t pa = (vma->vm_pgoff << PAGE_SHIFT) +
-					 vm_start - vma->vm_start;
+			phys_addr_t pa;
+
+			pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
+			pa += vm_start - vma->vm_start;
 
 			ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
 						    vm_end - vm_start,
-- 
1.9.1

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