[PATCH 3.16 176/346] MIPS: KVM: Add missing gfn range check

[Ben Hutchings <ben@xxxxxxxxxxxxxxx>]

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

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

From: James Hogan <james.hogan@xxxxxxxxxx>

commit 8985d50382359e5bf118fdbefc859d0dbf6cebc7 upstream.

kvm_mips_handle_mapped_seg_tlb_fault() calculates the guest frame number
based on the guest TLB EntryLo values, however it is not range checked
to ensure it lies within the guest_pmap. If the physical memory the
guest refers to is out of range then dump the guest TLB and emit an
internal error.

Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim Krčmář" <rkrcmar@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/mips/kvm/kvm_tlb.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

--- a/arch/mips/kvm/kvm_tlb.c
+++ b/arch/mips/kvm/kvm_tlb.c
@@ -361,6 +361,7 @@ kvm_mips_handle_mapped_seg_tlb_fault(str
 	unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;
 	struct kvm *kvm = vcpu->kvm;
 	pfn_t pfn0, pfn1;
+	gfn_t gfn0, gfn1;
 	long tlb_lo[2];
 
 
@@ -375,18 +376,24 @@ kvm_mips_handle_mapped_seg_tlb_fault(str
 			VPN2_MASK & (PAGE_MASK << 1)))
 		tlb_lo[(KVM_GUEST_COMMPAGE_ADDR >> PAGE_SHIFT) & 1] = 0;
 
-	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[0])
-				   >> PAGE_SHIFT) < 0)
+	gfn0 = mips3_tlbpfn_to_paddr(tlb_lo[0]) >> PAGE_SHIFT;
+	gfn1 = mips3_tlbpfn_to_paddr(tlb_lo[1]) >> PAGE_SHIFT;
+	if (gfn0 >= kvm->arch.guest_pmap_npages ||
+	    gfn1 >= kvm->arch.guest_pmap_npages) {
+		kvm_err("%s: Invalid gfn: [%#llx, %#llx], EHi: %#lx\n",
+			__func__, gfn0, gfn1, tlb->tlb_hi);
+		kvm_mips_dump_guest_tlbs(vcpu);
 		return -1;
+	}
 
-	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[1])
-				   >> PAGE_SHIFT) < 0)
+	if (kvm_mips_map_page(kvm, gfn0) < 0)
 		return -1;
 
-	pfn0 = kvm->arch.guest_pmap[
-		mips3_tlbpfn_to_paddr(tlb_lo[0]) >> PAGE_SHIFT];
-	pfn1 = kvm->arch.guest_pmap[
-		mips3_tlbpfn_to_paddr(tlb_lo[1]) >> PAGE_SHIFT];
+	if (kvm_mips_map_page(kvm, gfn1) < 0)
+		return -1;
+
+	pfn0 = kvm->arch.guest_pmap[gfn0];
+	pfn1 = kvm->arch.guest_pmap[gfn1];
 
 	if (hpa0)
 		*hpa0 = pfn0 << PAGE_SHIFT;