linux-kernel - [PATCH] HID: prodikeys: Check presence of pm->input

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Message-ID: <20260109105807.3141618-2-gnoack@google.com>
Date: Fri,  9 Jan 2026 11:58:08 +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: prodikeys: Check presence of pm->input_ep82

Fake USB devices can send their own report descriptors for which the
input_mapping() hook does not get called.  In this case, pm->input_ep82 stays
NULL, which leads to a crash later.

This does not happen with the real device, but can be provoked by imposing as
one.

Cc: stable@...r.kernel.org
Signed-off-by: Günther Noack <gnoack@...gle.com>
---
 drivers/hid/hid-prodikeys.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/hid-prodikeys.c b/drivers/hid/hid-prodikeys.c
index 74bddb2c3e82..6e413df38358 100644
--- a/drivers/hid/hid-prodikeys.c
+++ b/drivers/hid/hid-prodikeys.c
@@ -378,6 +378,10 @@ static int pcmidi_handle_report4(struct pcmidi_snd *pm, u8 *data)
 	bit_mask = (bit_mask << 8) | data[2];
 	bit_mask = (bit_mask << 8) | data[3];
 
+	/* robustness in case input_mapping hook does not get called */
+	if (!pm->input_ep82)
+		return 0;
+
 	/* break keys */
 	for (bit_index = 0; bit_index < 24; bit_index++) {
 		if (!((0x01 << bit_index) & bit_mask)) {
-- 
2.52.0.457.g6b5491de43-goog