Re: [PATCH v6 3/4] vsprintf: Use hw RNG for ptr_key

Steven Rostedt
2018-05-31T20:46:42Z

On Mon, 28 May 2018 11:46:41 +1000
"Tobin C. Harding" <me@tobin.cc> wrote:

> Currently we must wait for enough entropy to become available before
> hashed pointers can be printed. We can remove this wait by using the
> hw RNG if available.
>
> Use hw RNG to get keying material.
>
> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Tobin C. Harding <me@tobin.cc>
> ---
> lib/vsprintf.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 23920c5ff728..1545a8aa26a9 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1693,8 +1693,16 @@ static struct random_ready_callback random_ready = {
>
> static int __init initialize_ptr_random(void)
> {
> - int ret = add_random_ready_callback(&random_ready);
> + int key_size = sizeof(ptr_key);
> + int ret;
> +
> + /* Use hw RNG if available */
> + if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
> + static_branch_disable(&not_filled_random_ptr_key);
> + return 0;
> + }
>
> + ret = add_random_ready_callback(&random_ready);
> if (!ret) {
> return 0;
> } else if (ret == -EALREADY) {