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HID: wacom: Avoid using stale array indicies to read contact count

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commit 20f3cf5f86 upstream.

If we ever see a touch report with contact count data we initialize
several variables used to read the contact count in the pre-report
phase. These variables are never reset if we process a report which
doesn't contain a contact count, however. This can cause the pre-
report function to trigger a read of arbitrary memory (e.g. NULL
if we're lucky) and potentially crash the driver.

This commit restores resetting of the variables back to default
"none" values that were used prior to the commit mentioned
below.

Link: https://github.com/linuxwacom/input-wacom/issues/276
Fixes: 003f50ab67 (HID: wacom: Update last_slot_field during pre_report phase)
CC: stable@vger.kernel.org
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason Gerecke 2022-01-18 14:38:41 -08:00 committed by Greg Kroah-Hartman
parent 5e1715f50f
commit cc6ccfdaa7
1 changed files with 4 additions and 0 deletions
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4
drivers/hid/wacom_wac.c
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@ -2505,6 +2505,10 @@ static void wacom_wac_finger_pre_report(struct hid_device *hdev,
hid_data->confidence = true;
hid_data->cc_report = 0;
hid_data->cc_index = -1;
hid_data->cc_value_index = -1;
for (i = 0; i < report->maxfield; i++) {
struct hid_field *field = report->field[i];
int j;