FAILED: Patch "HID: prodikeys: Check presence of pm->input_ep82" failed to apply to 6.1-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From cee8337e1bad168136aecfe6416ecd7d3aa7529a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCnther=20Noack?= <gnoack@google.com>
Date: Fri, 9 Jan 2026 11:58:08 +0100
Subject: [PATCH] HID: prodikeys: Check presence of pm->input_ep82
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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@vger.kernel.org
Signed-off-by: Günther Noack <gnoack@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.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 74bddb2c3e82e..6e413df38358a 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)) {
-- 
2.51.0