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HID: provide a helper for validating hid reports

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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 <[email protected]>
Cc: [email protected]
Reviewed-by: Benjamin Tissoires <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>
This commit is contained in:
Kees Cook 2013-09-11 21:56:50 +02:00 • committed by Jiri Kosina
commit 331415ff16
2 changed files with 62 additions and 0 deletions
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58
drivers/hid/hid-core.c
View file

@ -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
*