Re: [PATCH 12/18] Thermal/int340x: prevent bounds-check bypass via speculative execution

Sergei Shtylyov
2018-01-06T10:03:25Z

On 1/6/2018 4:10 AM, Dan Williams wrote:

> Static analysis reports that 'trip' may be a user controlled value that
> is used as a data dependency to read '*temp' from the 'd->aux_trips'
> array. In order to avoid potential leaks of kernel memory values, block
> speculative execution of the instruction stream that could issue reads
> based on an invalid value of '*temp'.
>
> Based on an original patch by Elena Reshetova.
>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: Eduardo Valentin <edubezval@gmail.com>
> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> .../thermal/int340x_thermal/int340x_thermal_zone.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/thermal/int340x_thermal/int340x_thermal_zone.c b/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
> index 145a5c53ff5c..442a1d9bf7ad 100644
> --- a/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
> +++ b/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
[...]
> @@ -52,20 +53,21 @@ static int int340x_thermal_get_trip_temp(struct thermal_zone_device *zone,
> int trip, int *temp)
> {
> struct int34x_thermal_zone *d = zone->devdata;
> + unsigned long *elem;
> int i;
>
> if (d->override_ops && d->override_ops->get_trip_temp)
> return d->override_ops->get_trip_temp(zone, trip, temp);
>
> - if (trip < d->aux_trip_nr)
> - *temp = d->aux_trips[trip];
> - else if (trip == d->crt_trip_id)
> + if ((elem = nospec_array_ptr(d->aux_trips, trip, d->aux_trip_nr))) {

And here...

> + *temp = *elem;
> + } else if (trip == d->crt_trip_id) {
> *temp = d->crt_temp;
> - else if (trip == d->psv_trip_id)
> + } else if (trip == d->psv_trip_id) {
> *temp = d->psv_temp;
> - else if (trip == d->hot_trip_id)
> + } else if (trip == d->hot_trip_id) {
> *temp = d->hot_temp;
> - else {
> + } else {
> for (i = 0; i < INT340X_THERMAL_MAX_ACT_TRIP_COUNT; i++) {
> if (d->act_trips[i].valid &&
> d->act_trips[i].id == trip) {

MBR, Sergei