[ 09/49] HID: provide a helper for validating hid reports

Greg Kroah-Hartman
2013-09-29T19:51:44Z

From: Kees Cook <keescook@chromium.org>

commit 331415ff16a12147d57d5c953f3a961b7ede348b upstream.

Many drivers need to validate the characteristics of their HID report
during initialization to avoid misusing the reports. This adds a common
helper to perform validation of the report exisitng, the field existing,
and the expected number of values within the field.

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

---
drivers/hid/hid-core.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/hid.h | 4 +++
2 files changed, 62 insertions(+)

--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -759,6 +759,64 @@ int hid_parse_report(struct hid_device *
}
EXPORT_SYMBOL_GPL(hid_parse_report);

+static const char * const hid_report_names[] = {
+ "HID_INPUT_REPORT",
+ "HID_OUTPUT_REPORT",
+ "HID_FEATURE_REPORT",
+};
+/**
+ * hid_validate_values - validate existing device report's value indexes
+ *
+ * @device: hid device
+ * @type: which report type to examine
+ * @id: which report ID to examine (0 for first)
+ * @field_index: which report field to examine
+ * @report_counts: expected number of values
+ *
+ * Validate the number of values in a given field of a given report, after
+ * parsing.
+ */
+struct hid_report *hid_validate_values(struct hid_device *hid,
+ unsigned int type, unsigned int id,
+ unsigned int field_index,
+ unsigned int report_counts)
+{
+ struct hid_report *report;
+
+ if (type > HID_FEATURE_REPORT) {
+ hid_err(hid, "invalid HID report type %u\n", type);
+ return NULL;
+ }
+
+ if (id >= HID_MAX_IDS) {
+ hid_err(hid, "invalid HID report id %u\n", id);
+ return NULL;
+ }
+
+ /*
+ * Explicitly not using hid_get_report() here since it depends on
+ * ->numbered being checked, which may not always be the case when
+ * drivers go to access report values.
+ */
+ report = hid->report_enum[type].report_id_hash[id];
+ if (!report) {
+ hid_err(hid, "missing %s %u\n", hid_report_names[type], id);
+ return NULL;
+ }
+ if (report->maxfield <= field_index) {
+ hid_err(hid, "not enough fields in %s %u\n",
+ hid_report_names[type], id);
+ return NULL;
+ }
+ if (report->field[field_index]->report_count < report_counts) {
+ hid_err(hid, "not enough values in %s %u field %u\n",
+ hid_report_names[type], id, field_index);
+ return NULL;
+ }
+ return report;
+}
+EXPORT_SYMBOL_GPL(hid_validate_values);
+
/**
* hid_open_report - open a driver-specific device report
*
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -749,6 +749,10 @@ void hid_output_report(struct hid_report
struct hid_device *hid_allocate_device(void);
struct hid_report *hid_register_report(struct hid_device *device, unsigned type, unsigned id);
int hid_parse_report(struct hid_device *hid, __u8 *start, unsigned size);
+struct hid_report *hid_validate_values(struct hid_device *hid,
+ unsigned int type, unsigned int id,
+ unsigned int field_index,
+ unsigned int report_counts);
int hid_open_report(struct hid_device *device);
int hid_check_keys_pressed(struct hid_device *hid);
int hid_connect(struct hid_device *hid, unsigned int connect_mask);