Re: [PATCH v3 05/11] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command

[Peter Gonda <pgonda@google.com>]

> +
> +       /* Check if we are crossing the page boundry */
> +       offset = params.guest_uaddr & (PAGE_SIZE - 1);
> +       if ((params.guest_len + offset > PAGE_SIZE))
> +               return -EINVAL;

Just curious spec only says that "System physical of the guest memory
region. Must be 16 B aligned with the C-bit set." and "Length of guest
memory region. Must be a multiple of 16 B and no more than 16 kB". Why
do we want to avoid crossing a page boundary?

Also is there an overflow concern in the conditional because
params.guest_len is not checked before this?

> +
> +       data = kzalloc(sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);
> +       if (IS_ERR(hdr)) {
> +               ret = PTR_ERR(hdr);
> +               goto e_free;
> +       }
> +