linux-kernel - [PATCH] HID: input: set usage type to key on keycode remap

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Message-Id: <20211028205542.499280-1-linux@weissschuh.net>
Date:   Thu, 28 Oct 2021 22:55:42 +0200
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Thomas Weißschuh <linux@...ssschuh.net>,
        linux-kernel@...r.kernel.org, Brent Roman <brent@...ri.org>
Subject: [PATCH] HID: input: set usage type to key on keycode remap

When a scancode is manually remapped that previously was not handled as
key, then the old usage type was incorrectly reused.

This caused issues on a "04b3:301b IBM Corp. SK-8815 Keyboard" which has
marked some of its keys with an invalid HID usage.  These invalid usage
keys are being ignored since support for USB programmable buttons was
added.

The scancodes are however remapped explicitly by the systemd hwdb to the
keycodes that are printed on the physical buttons.  During this mapping
step the existing usage is retrieved which will be found with a default
type of 0 (EV_SYN) instead of EV_KEY.

The events with the correct code but EV_SYN type are not forwarded to
userspace.

This also leads to a kernel oops when trying to print the report descriptor
via debugfs.  hid_resolv_event() tries to resolve a EV_SYN event with an
EV_KEY code which leads to an out-of-bounds access in the EV_SYN names
array.

Fixes: bcfa8d1457 ("HID: input: Add support for Programmable Buttons")
Fixes: f5854fad39 ("Input: hid-input - allow mapping unknown usages")
Reported-by: Brent Roman <brent@...ri.org>
Tested-by: Brent Roman <brent@...ri.org>
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 drivers/hid/hid-input.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 4b5ebeacd283..21d8cc64064d 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -160,6 +160,7 @@ static int hidinput_setkeycode(struct input_dev *dev,
 	if (usage) {
 		*old_keycode = usage->type == EV_KEY ?
 				usage->code : KEY_RESERVED;
+		usage->type = EV_KEY;
 		usage->code = ke->keycode;

 		clear_bit(*old_keycode, dev->keybit);

base-commit: 42d43c92fc577dca59ed74aec7868abec8d6ca6e
-- 
2.33.1