From 2d3f53a80e4eed078669853a178ed96d88f74143 Mon Sep 17 00:00:00 2001
From: Rodrigo Rivas Costa <rodrigorivascosta@gmail.com>
Date: Tue, 16 Jun 2020 18:44:18 +0200
Subject: [PATCH] HID: steam: fixes race in handling device list.
Git-commit: 2d3f53a80e4eed078669853a178ed96d88f74143
Patch-mainline: v5.8-rc6
References: git-fixes

Using uhid and KASAN this driver crashed because it was getting
several connection events where it only expected one. Then the
device was added several times to the static device list and it got
corrupted.

This patch checks if the device is already in the list before adding
it.

Signed-off-by: Rodrigo Rivas Costa <rodrigorivascosta@gmail.com>
Tested-by: Siarhei Vishniakou <svv@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/hid/hid-steam.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-steam.c b/drivers/hid/hid-steam.c
index 6286204d4c56..a3b151b29bd7 100644
--- a/drivers/hid/hid-steam.c
+++ b/drivers/hid/hid-steam.c
@@ -526,7 +526,8 @@ static int steam_register(struct steam_device *steam)
 			steam_battery_register(steam);
 
 		mutex_lock(&steam_devices_lock);
-		list_add(&steam->list, &steam_devices);
+		if (list_empty(&steam->list))
+			list_add(&steam->list, &steam_devices);
 		mutex_unlock(&steam_devices_lock);
 	}
 
@@ -552,7 +553,7 @@ static void steam_unregister(struct steam_device *steam)
 		hid_info(steam->hdev, "Steam Controller '%s' disconnected",
 				steam->serial_no);
 		mutex_lock(&steam_devices_lock);
-		list_del(&steam->list);
+		list_del_init(&steam->list);
 		mutex_unlock(&steam_devices_lock);
 		steam->serial_no[0] = 0;
 	}
@@ -738,6 +739,7 @@ static int steam_probe(struct hid_device *hdev,
 	mutex_init(&steam->mutex);
 	steam->quirks = id->driver_data;
 	INIT_WORK(&steam->work_connect, steam_work_connect_cb);
+	INIT_LIST_HEAD(&steam->list);
 
 	steam->client_hdev = steam_create_client_hid(hdev);
 	if (IS_ERR(steam->client_hdev)) {
-- 
2.16.4