KVM: x86: 32-bit wraparound read/write not emulated correctly

If we got a wraparound of 32-bit operand, and the limit is 0xffffffff, read and
writes should be successful. It just needs to be done in two segments.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 9 insertions, 3 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 997c9ebb70ef..c3b07574942f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -684,9 +684,13 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
                 }
                 if (addr.ea > lim)
                         goto bad;
-                *max_size = min_t(u64, ~0u, (u64)lim + 1 - addr.ea);
-                if (size > *max_size)
-                        goto bad;
+                if (lim == 0xffffffff)
+                        *max_size = ~0u;
+                else {
+                        *max_size = (u64)lim + 1 - addr.ea;
+                        if (size > *max_size)
+                                goto bad;
+                }
                 la &= (u32)-1;
                 break;
         }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cdd6606e4c54..1e10e3f7f516 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4495,6 +4495,8 @@ int emulator_read_write(struct x86_emulate_ctxt *ctxt, unsigned long addr,
                 if (rc != X86EMUL_CONTINUE)
                         return rc;
                 addr += now;
+                if (ctxt->mode != X86EMUL_MODE_PROT64)
+                        addr = (u32)addr;
                 val += now;
                 bytes -= now;
         }