HID: logitech-dj: fix wrong detection of bad DJ_SHORT output report

commit b6a57912854e ("HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT
related user initiated OOB write") assumed that all HID devices attached
to the logitech-dj driver was having an output report of DJ_SHORT.

However, on the receiver itself, we have 2 other HID device we attach
here: the mouse emulation and the keyboard emulation. For those devices
the value of rep is NULL and we are triggered a segfault here.

This is doubly required because logitech-dj also handles non DJ devices
that might not have the DJ collection.

Fixes: b6a57912854e ("HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT related user initiated OOB write")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
index 838c6de9a921c534cf28e167be32192f7ba5601d..695d3031009e1c6299d1813b34cbb4290c888fd7 100644 (file)
--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -1907,7 +1907,8 @@ static int logi_dj_probe(struct hid_device *hdev,
        output_report_enum = &hdev->report_enum[HID_OUTPUT_REPORT];
        rep = output_report_enum->report_id_hash[REPORT_ID_DJ_SHORT];
 
-       if (rep->maxfield < 1 || rep->field[0]->report_count != DJREPORT_SHORT_LENGTH - 1) {
+       if (rep && (rep->maxfield < 1 ||
+                   rep->field[0]->report_count != DJREPORT_SHORT_LENGTH - 1)) {
                hid_err(hdev, "Expected size of DJ short report is %d, but got %d",
                        DJREPORT_SHORT_LENGTH - 1, rep->field[0]->report_count);
                return -EINVAL;