From 331415ff16a12147d57d5c953f3a961b7ede348b Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 11 Sep 2013 21:56:50 +0200 Subject: [PATCH] HID: provide a helper for validating hid reports 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 Cc: stable@vger.kernel.org Reviewed-by: Benjamin Tissoires Signed-off-by: Jiri Kosina --- drivers/hid/hid-core.c | 58 ++++++++++++++++++++++++++++++++++++++++++ include/linux/hid.h | 4 +++ 2 files changed, 62 insertions(+) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index ae88a97f976e..be52c06dbe30 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -801,6 +801,64 @@ int hid_parse_report(struct hid_device *hid, __u8 *start, unsigned size) } 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 * diff --git a/include/linux/hid.h b/include/linux/hid.h index ee1ffc5e19c9..31b9d299ef6c 100644 --- a/include/linux/hid.h +++ b/include/linux/hid.h @@ -756,6 +756,10 @@ u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags); 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); -- 2.20.1