linux-kernel - [PATCH] HID: magicmouse: Do not crash on missing msc->input

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Message-ID: <20260109105714.3140851-2-gnoack@google.com>
Date: Fri,  9 Jan 2026 11:57:14 +0100
From: "Günther Noack" <gnoack@...gle.com>
To: Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <bentiss@...nel.org>
Cc: "Günther Noack" <gnoack@...gle.com>, stable@...r.kernel.org, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] HID: magicmouse: Do not crash on missing msc->input

Fake USB devices can send their own report descriptors for which the
input_mapping() hook does not get called.  In this case, msc->input stays NULL,
leading to a crash at a later time.

Detect this condition in the input_configured() hook and reject the device.

This is not supposed to happen with actual magic mouse devices, but can be
provoked by imposing as a magic mouse USB device.

Cc: stable@...r.kernel.org
Signed-off-by: Günther Noack <gnoack@...gle.com>
---
 drivers/hid/hid-magicmouse.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 6e7c189f4d1d..b8932f02b6ee 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -726,6 +726,11 @@ static int magicmouse_input_configured(struct hid_device *hdev,
 	struct magicmouse_sc *msc = hid_get_drvdata(hdev);
 	int ret;
 
+	if (!msc->input) {
+		hid_err(hdev, "magicmouse setup input failed (no input)");
+		return -EINVAL;
+	}
+
 	ret = magicmouse_setup_input(msc->input, hdev);
 	if (ret) {
 		hid_err(hdev, "magicmouse setup input failed (%d)\n", ret);
-- 
2.52.0.457.g6b5491de43-goog