[PATCH] HID: nintendo: check analog user calibration for plausibility

[Johnothan King]

Arne Wendt writes:
  Cheap clone controllers may (falsely) report as having a user
  calibration for the analog sticks in place, but return
  wrong/impossible values for the actual calibration data.
  In the present case at mine, the controller reports having a
  user calibration in place and successfully executes the read
  commands. The reported user calibration however is
  min = center = max = 0.

  This pull request addresses problems of this kind by checking the
  provided user calibration-data for plausibility (min < center < max)
  and falling back to the default values if implausible.

I'll note that I was experiencing a crash because of this bug when using
the GuliKit KingKong 2 controller. The crash manifests as a divide by
zero error in the kernel logs:
kernel: divide error: 0000 [#1] PREEMPT SMP NOPTI

Link: https://github.com/nicman23/dkms-hid-nintendo/pull/25
Link: https://github.com/DanielOgorchock/linux/issues/36
Co-authored-by: Arne Wendt <arne.wendt@xxxxxxx>
Signed-off-by: Johnothan King <johnothanking@xxxxxxxxxxxxxx>
---
 drivers/hid/hid-nintendo.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-nintendo.c b/drivers/hid/hid-nintendo.c
index 6028af3c3aae..7f287f6a75f5 100644
--- a/drivers/hid/hid-nintendo.c
+++ b/drivers/hid/hid-nintendo.c
@@ -793,7 +793,17 @@ static int joycon_request_calibration(struct joycon_ctlr *ctlr)
 					    &ctlr->left_stick_cal_x,
 					    &ctlr->left_stick_cal_y,
 					    true);
-	if (ret) {
+
+	/*
+	 * Check whether read succeeded and perform plausibility check
+	 * for retrieved values.
+	 */
+	if (ret ||
+		ctlr->left_stick_cal_x.min >= ctlr->left_stick_cal_x.center ||
+		ctlr->left_stick_cal_x.center >= ctlr->left_stick_cal_x.max ||
+		ctlr->left_stick_cal_y.min >= ctlr->left_stick_cal_y.center ||
+		ctlr->left_stick_cal_y.center >= ctlr->left_stick_cal_y.max
+	) {
 		hid_warn(ctlr->hdev,
 			 "Failed to read left stick cal, using dflts; e=%d\n",
 			 ret);
@@ -812,7 +822,17 @@ static int joycon_request_calibration(struct joycon_ctlr *ctlr)
 					    &ctlr->right_stick_cal_x,
 					    &ctlr->right_stick_cal_y,
 					    false);
-	if (ret) {
+
+	/*
+	 * Check whether read succeeded and perform plausibility check
+	 * for retrieved values.
+	 */
+	if (ret ||
+		ctlr->right_stick_cal_x.min >= ctlr->right_stick_cal_x.center ||
+		ctlr->right_stick_cal_x.center >= ctlr->right_stick_cal_x.max ||
+		ctlr->right_stick_cal_y.min >= ctlr->right_stick_cal_y.center ||
+		ctlr->right_stick_cal_y.center >= ctlr->right_stick_cal_y.max
+	) {
 		hid_warn(ctlr->hdev,
 			 "Failed to read right stick cal, using dflts; e=%d\n",
 			 ret);
-- 
2.37.3