linux-kernel - [PATCH v1] HID: make arrays usage and value to be the same

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Message-Id: <20201205004848.2541215-1-willmcvicker@google.com>
Date:   Sat,  5 Dec 2020 00:48:48 +0000
From:   Will McVicker <willmcvicker@...gle.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        security@...nel.org
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Will Coster <willcoster@...gle.com>,
        Will McVicker <willmcvicker@...gle.com>
Subject: [PATCH v1] HID: make arrays usage and value to be the same

The HID subsystem allows an "HID report field" to have a different
number of "values" and "usages" when it is allocated. When a field
struct is created, the size of the usage array is guaranteed to be at
least as large as the values array, but it may be larger. This leads to
a potential out-of-bounds write in
__hidinput_change_resolution_multipliers() and an out-of-bounds read in
hidinput_count_leds().

To fix this, let's make sure that both the usage and value arrays are
the same size.

Signed-off-by: Will McVicker <willmcvicker@...gle.com>
---
 drivers/hid/hid-core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 56172fe6995c..8a8b2b982f83 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -90,7 +90,7 @@ EXPORT_SYMBOL_GPL(hid_register_report);
  * Register a new field for this report.
  */
 
-static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages, unsigned values)
+static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages)
 {
 	struct hid_field *field;
 
@@ -101,7 +101,7 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
 
 	field = kzalloc((sizeof(struct hid_field) +
 			 usages * sizeof(struct hid_usage) +
-			 values * sizeof(unsigned)), GFP_KERNEL);
+			 usages * sizeof(unsigned)), GFP_KERNEL);
 	if (!field)
 		return NULL;
 
@@ -300,7 +300,7 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
 	usages = max_t(unsigned, parser->local.usage_index,
 				 parser->global.report_count);
 
-	field = hid_register_field(report, usages, parser->global.report_count);
+	field = hid_register_field(report, usages);
 	if (!field)
 		return 0;
 
-- 
2.29.2.576.ga3fc446d84-goog