zero-extend usage page before copying shorter payload

1 files changed, 6 insertions, 1 deletions

diff --git a/src/class/hid/hid_host.c b/src/class/hid/hid_host.c
index bd419c72d..29bcae99f 100644
--- a/src/class/hid/hid_host.c
+++ b/src/class/hid/hid_host.c
@@ -742,7 +742,12 @@ uint8_t tuh_hid_parse_report_descriptor(tuh_hid_report_info_t* report_info_arr,
         switch (tag) {
           case RI_GLOBAL_USAGE_PAGE:
             // only take in account the "usage page" before REPORT ID
-            if (ri_collection_depth == 0) memcpy(&info->usage_page, desc_report, TU_MIN(size, sizeof(info->usage_page)));
+            if (ri_collection_depth == 0) {
+              // zero-extend: a shorter payload must not leave a stale high byte
+              // from a previous usage page item in the same report
+              info->usage_page = 0;
+              memcpy(&info->usage_page, desc_report, TU_MIN(size, sizeof(info->usage_page)));
+            }
             break;
 
           case RI_GLOBAL_LOGICAL_MIN: break;