From ed9be64eefe26d7d8b0b5b9fa3ffdf425d87a01f Mon Sep 17 00:00:00 2001
From: Will McVicker <willmcvicker@google.com>
Date: Sat, 5 Dec 2020 00:48:48 +0000
Subject: [PATCH] HID: make arrays usage and value to be the same
Git-commit: ed9be64eefe26d7d8b0b5b9fa3ffdf425d87a01f
Patch-mainline: v5.12-rc1
References: git-fixes

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.

Cc: stable@vger.kernel.org
Signed-off-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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 4d0faf77c14b..097cb1ee3126 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;
 
-- 
2.26.2