[PATCH] HID: hid-input: clear unmapped usages

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

We should not be leaving half-mapped usages with potentially invalid
keycodes, as that may confuse hidinput_find_key() when the key is
located by index, which may end up feeding way too large keycode into
the VT keyboard handler and cause OOB write there:

BUG: KASAN: global-out-of-bounds in clear_bit include/asm-generic/bitops-instrumented.h:56 [inline]
BUG: KASAN: global-out-of-bounds in kbd_keycode drivers/tty/vt/keyboard.c:1411 [inline]
BUG: KASAN: global-out-of-bounds in kbd_event+0xe6b/0x3790 drivers/tty/vt/keyboard.c:1495
Write of size 8 at addr ffffffff89a1b2d8 by task syz-executor108/1722
...
 kbd_keycode drivers/tty/vt/keyboard.c:1411 [inline]
 kbd_event+0xe6b/0x3790 drivers/tty/vt/keyboard.c:1495
 input_to_handler+0x3b6/0x4c0 drivers/input/input.c:118
 input_pass_values.part.0+0x2e3/0x720 drivers/input/input.c:145
 input_pass_values drivers/input/input.c:949 [inline]
 input_set_keycode+0x290/0x320 drivers/input/input.c:954
 evdev_handle_set_keycode_v2+0xc4/0x120 drivers/input/evdev.c:882
 evdev_do_ioctl drivers/input/evdev.c:1150 [inline]

In this case we were dealing with a fuzzed HID device that declared over
12K buttons:

https://syzkaller.appspot.com/bug?extid=19340dff067c2d3835c0

Reported-by: syzbot+19340dff067c2d3835c0@syzkaller.appspotmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---

I'll be putting a guard into drivers/tty/vt/keyboard.c as well.
Please consider for stable.

 drivers/hid/hid-input.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 63855f275a38..3957d1c4d967 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1215,9 +1215,11 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 		set_bit(MSC_SCAN, input->mscbit);
 	}
 
-ignore:
 	return;
 
+ignore:
+	usage->type = 0;
+	usage->code = 0;
 }
 
 static void hidinput_handle_scroll(struct hid_usage *usage,
-- 
2.24.0.432.g9d3f5f5b63-goog


-- 
Dmitry