From 4f3882177240a1f55e45a3d241d3121341bead78 Mon Sep 17 00:00:00 2001
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: Sat, 7 Dec 2019 13:05:18 -0800
Subject: [PATCH] HID: hid-input: clear unmapped usages
Git-commit: 4f3882177240a1f55e45a3d241d3121341bead78
Patch-mainline: v5.5-rc6
References: CVE-2020-0431 bsc#1176722

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]

Cc: stable@vger.kernel.org
Reported-by: syzbot+19340dff067c2d3835c0@syzkaller.appspotmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/hid/hid-input.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1031,9 +1031,15 @@ static void hidinput_configure_usage(str
 	}
 
 mapped:
-	if (device->driver->input_mapped && device->driver->input_mapped(device,
-				hidinput, field, usage, &bit, &max) < 0)
-		goto ignore;
+	if (device->driver->input_mapped &&
+	    device->driver->input_mapped(device, hidinput, field, usage,
+					 &bit, &max) < 0) {
+		/*
+		 * The driver indicated that no further generic handling
+		 * of the usage is desired.
+		 */
+		return;
+	}
 
 	set_bit(usage->type, input->evbit);
 
@@ -1092,9 +1098,11 @@ mapped:
 		set_bit(MSC_SCAN, input->mscbit);
 	}
 
-ignore:
 	return;
 
+ignore:
+	usage->type = 0;
+	usage->code = 0;
 }
 
 void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct hid_usage *usage, __s32 value)