[PATCH 3.8 021/116] HID: core: fix validation of report id 0

[Kamal Mostafa]

3.8.13.27 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook at chromium.org>

commit 1b15d2e5b8077670b1e6a33250a0d9577efff4a5 upstream.

Some drivers use the first HID report in the list instead of using an
index. In these cases, validation uses ID 0, which was supposed to mean
"first known report". This fixes the problem, which was causing at least
the lgff family of devices to stop working since hid_validate_values
was being called with ID 0, but the devices used single numbered IDs
for their reports:

0x05, 0x01,         /*  Usage Page (Desktop),                   */
0x09, 0x05,         /*  Usage (Gamepad),                        */
0xA1, 0x01,         /*  Collection (Application),               */
0xA1, 0x02,         /*      Collection (Logical),               */
0x85, 0x01,         /*          Report ID (1),                  */
...

Reported-by: Simon Wood <simon at mungewell.org>
Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires at redhat.com>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/hid/hid-core.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 14744e0..8ad2505 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -797,7 +797,17 @@ struct hid_report *hid_validate_values(struct hid_device *hid,
 	 * ->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 (id == 0) {
+		/*
+		 * Validating on id 0 means we should examine the first
+		 * report in the list.
+		 */
+		report = list_entry(
+				hid->report_enum[type].report_list.next,
+				struct hid_report, list);
+	} else {
+		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;
-- 
1.9.1