[PATCH v2] HID: magicmouse: fix null pointer dereference in magicmouse_event()

Add a guard clause to check if 'msc' and 'msc->input' is NULL
before attempting to access its fields, preventing a general
protection fault.

Fixes: b8d56ef91cc3 ("HID: magicmouse: Apple Magic Mouse 2 USB-C support")
Reported-by: syzbot+5ad4fc9c8360b68e353f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5ad4fc9c8360b68e353f
Signed-off-by: Nehuen Lian Bova <redacted>
---
Changes in v2:
 - Also check msc->input before dereferencing it, not just msc

 drivers/hid/hid-magicmouse.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index d637c0477379..e6d4d4930526 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c

@@ -553,6 +553,10 @@ static int magicmouse_event(struct hid_device *hdev, struct hid_field *field,
 		struct hid_usage *usage, __s32 value)
 {
 	struct magicmouse_sc *msc = hid_get_drvdata(hdev);
+
+	if (!msc || !msc->input)
+		return 0;
+
 	if ((msc->input->id.product == USB_DEVICE_ID_APPLE_MAGICMOUSE2 ||
 	     msc->input->id.product == USB_DEVICE_ID_APPLE_MAGICMOUSE2_USBC) &&
 	    field->report->id == MOUSE2_REPORT_ID) {

-- 
2.43.0