[PATCH 3.16 112/245] HID: hid-input: clear unmapped usages

Ben Hutchings
2020-04-23T23:15:22Z

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>

commit 4f3882177240a1f55e45a3d241d3121341bead78 upstream.

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]

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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
@@ -947,9 +947,15 @@ 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);

@@ -1008,9 +1014,11 @@ 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)