HID: betop: check shape of output reports

betopff_init() only checks the total sum of the report counts for each
report field to be at least 4, but hid_betopff_play() expects 4 report
fields.
A device advertising an output report with one field and 4 report counts
would pass the check but crash the kernel with a NULL pointer dereference
in hid_betopff_play().

Fixes: 52cd7785f3cd ("HID: betop: add drivers/hid/hid-betopff.c")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-betopff.c b/drivers/hid/hid-betopff.c
index 467d789..25ed7b9 100644 (file)
--- a/drivers/hid/hid-betopff.c
+++ b/drivers/hid/hid-betopff.c
@@ -60,7 +60,6 @@ static int betopff_init(struct hid_device *hid)
        struct list_head *report_list =
                        &hid->report_enum[HID_OUTPUT_REPORT].report_list;
        struct input_dev *dev;
-       int field_count = 0;
        int error;
        int i, j;
 
@@ -86,19 +85,21 @@ static int betopff_init(struct hid_device *hid)
         * -----------------------------------------
         * Do init them with default value.
         */
+       if (report->maxfield < 4) {
+               hid_err(hid, "not enough fields in the report: %d\n",
+                               report->maxfield);
+               return -ENODEV;
+       }
        for (i = 0; i < report->maxfield; i++) {
+               if (report->field[i]->report_count < 1) {
+                       hid_err(hid, "no values in the field\n");
+                       return -ENODEV;
+               }
                for (j = 0; j < report->field[i]->report_count; j++) {
                        report->field[i]->value[j] = 0x00;
-                       field_count++;
                }
        }
 
-       if (field_count < 4) {
-               hid_err(hid, "not enough fields in the report: %d\n",
-                               field_count);
-               return -ENODEV;
-       }
-
        betopff = kzalloc(sizeof(*betopff), GFP_KERNEL);
        if (!betopff)
                return -ENOMEM;