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>

1 files changed, 2 insertions, 3 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fe5474aec41a..7bc311464fae 100644
--- a/arch/x86/kvm/x86.c
+++ b/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;