[ 11/49] HID: multitouch: validate indexes details

Greg Kroah-Hartman
2013-09-29T19:27:56Z

From: Benjamin Tissoires <benjamin.tissoires@redhat.com>

commit 8821f5dc187bdf16cfb32ef5aa8c3035273fa79a upstream.

When working on report indexes, always validate that they are in bounds.
Without this, a HID device could report a malicious feature report that
could trick the driver into a heap overflow:

[ 634.885003] usb 1-1: New USB device found, idVendor=0596, idProduct=0500
...
[ 676.469629] BUG kmalloc-192 (Tainted: G W ): Redzone overwritten

Note that we need to change the indexes from s8 to s16 as they can
be between -1 and 255.

CVE-2013-2897

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hid/hid-multitouch.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)

--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -101,9 +101,9 @@ struct mt_device {
unsigned last_slot_field; /* the last field of a slot */
unsigned mt_report_id; /* the report ID of the multitouch device */
unsigned pen_report_id; /* the report ID of the pen device */
- __s8 inputmode; /* InputMode HID feature, -1 if non-existent */
- __s8 inputmode_index; /* InputMode HID feature index in the report */
- __s8 maxcontact_report_id; /* Maximum Contact Number HID feature,
+ __s16 inputmode; /* InputMode HID feature, -1 if non-existent */
+ __s16 inputmode_index; /* InputMode HID feature index in the report */
+ __s16 maxcontact_report_id; /* Maximum Contact Number HID feature,
-1 if non-existent */
__u8 num_received; /* how many contacts we received */
__u8 num_expected; /* expected last contact index */
@@ -317,20 +317,18 @@ static void mt_feature_mapping(struct hi
struct hid_field *field, struct hid_usage *usage)
{
struct mt_device *td = hid_get_drvdata(hdev);
- int i;

switch (usage->hid) {
case HID_DG_INPUTMODE:
- td->inputmode = field->report->id;
- td->inputmode_index = 0; /* has to be updated below */
-
- for (i=0; i < field->maxusage; i++) {
- if (field->usage[i].hid == usage->hid) {
- td->inputmode_index = i;
- break;
- }
+ /* Ignore if value index is out of bounds. */
+ if (usage->usage_index >= field->report_count) {
+ dev_err(&hdev->dev, "HID_DG_INPUTMODE out of range\n");
+ break;
}

+ td->inputmode = field->report->id;
+ td->inputmode_index = usage->usage_index;
+
break;
case HID_DG_CONTACTMAX:
td->maxcontact_report_id = field->report->id;
@@ -536,6 +534,10 @@ static int mt_touch_input_mapping(struct
mt_store_field(usage, td, hi);
return 1;
case HID_DG_CONTACTCOUNT:
+ /* Ignore if indexes are out of bounds. */
+ if (field->index >= field->report->maxfield ||
+ usage->usage_index >= field->report_count)
+ return 1;
td->cc_index = field->index;
td->cc_value_index = usage->usage_index;
return 1;