KVM: Fix KVM_GET_MSR_INDEX_LIST

So far, KVM copied the emulated_msrs (only MSR_IA32_MISC_ENABLE) to a
wrong address in user space due to broken pointer arithmetic. This
caused subtle corruption up there (missing MSR_IA32_MISC_ENABLE had
probably no practical relevance). Moreover, the size check for the
user-provided kvm_msr_list forgot about emulated MSRs.

Cc: stable@kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/x86.c

@@ -1079,14 +1079,13 @@ long kvm_arch_dev_ioctl(struct file *filp,
 		if (copy_to_user(user_msr_list, &msr_list, sizeof msr_list))
 			goto out;
 		r = -E2BIG;
-		if (n < num_msrs_to_save)
+		if (n < msr_list.nmsrs)
 			goto out;
 		r = -EFAULT;
 		if (copy_to_user(user_msr_list->indices, &msrs_to_save,
 				 num_msrs_to_save * sizeof(u32)))
 			goto out;
-		if (copy_to_user(user_msr_list->indices
-				 + num_msrs_to_save * sizeof(u32),
+		if (copy_to_user(user_msr_list->indices + num_msrs_to_save,
 				 &emulated_msrs,
 				 ARRAY_SIZE(emulated_msrs) * sizeof(u32)))
 			goto out;