uref->usage_index can be indirectly controlled by userspace, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.
This field is used as an array index by the hiddev_ioctl_usage() function,
when 'cmd' is either HIDIOCGCOLLECTIONINDEX, HIDIOCGUSAGES or
HIDIOCSUSAGES.
For cmd == HIDIOCGCOLLECTIONINDEX case, uref->usage_index is compared to
field->maxusage and then used as an index to dereference field->usage
array. The same thing happens to the cmd == HIDIOC{G,S}USAGES cases, where
uref->usage_index is checked against an array maximum value and then it is
used as an index in an array.
This is a summary of the HIDIOCGCOLLECTIONINDEX case, which matches the
traditional Spectre V1 first load:
copy_from_user(uref, user_arg, sizeof(*uref))
if (uref->usage_index >= field->maxusage)
goto inval;
i = field->usage[uref->usage_index].collection_index;
return i;
This patch fixes this by sanitizing field uref->usage_index before using it
to index field->usage (HIDIOCGCOLLECTIONINDEX) or field->value in
HIDIOC{G,S}USAGES arrays, thus, avoiding speculation in the first load.
Signed-off-by: Breno Leitao <[email protected]>
Cc: <[email protected]>
--
v2: Contemplate cmd == HIDIOC{G,S}USAGES case
diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 23872d08308c..a746017fac17 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -512,14 +512,24 @@ static noinline int hiddev_ioctl_usage(struct hiddev
*hiddev, unsigned int cmd,
if (cmd == HIDIOCGCOLLECTIONINDEX) {
if (uref->usage_index >= field->maxusage)
goto inval;
+ uref->usage_index =
+ array_index_nospec(uref->usage_index,
+ field->maxusage);
} else if (uref->usage_index >= field->report_count)
goto inval;
}
- if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) &&
- (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
- uref->usage_index + uref_multi->num_values >
field->report_count))
- goto inval;
+ if (cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) {
+ if (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
+ uref->usage_index + uref_multi->num_values >
+ field->report_count)
+ goto inval;
+
+ uref->usage_index =
+ array_index_nospec(uref->usage_index,
+ field->report_count -
+ uref_multi->num_values);
+ }
switch (cmd) {
case HIDIOCGUSAGE:
--
2.17.1
