[PATCH HID 2/3] HID: multitouch: Correct devm device reference for hidinput input_dev name

[Rahul Rameshbabu <sergeantsagara@protonmail.com>]

Reference the HID device rather than the input device for the devm
allocation of the input_dev name. Referencing the input_dev would lead to a
use-after-free when the input_dev was unregistered and subsequently fires a
uevent that depends on the name. At the point of firing the uevent, the
name would be freed by devres management.

Use devm_kasprintf to simplify the logic for allocating memory and
formatting the input_dev name string.

Reported-by: Maxime Ripard <mripard@kernel.org>
Closes: https://lore.kernel.org/linux-input/ZOZIZCND+L0P1wJc@penguin/T/#m443f3dce92520f74b6cf6ffa8653f9c92643d4ae
Fixes: c08d46aa805b ("HID: multitouch: devm conversion")
Suggested-by: Maxime Ripard <mripard@kernel.org>
Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>
---
 drivers/hid/hid-multitouch.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index e31be0cb8b85..521b2ffb4244 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1594,7 +1594,6 @@ static void mt_post_parse(struct mt_device *td, struct mt_application *app)
 static int mt_input_configured(struct hid_device *hdev, struct hid_input *hi)
 {
 	struct mt_device *td = hid_get_drvdata(hdev);
-	char *name;
 	const char *suffix = NULL;
 	struct mt_report_data *rdata;
 	struct mt_application *mt_application = NULL;
@@ -1645,15 +1644,9 @@ static int mt_input_configured(struct hid_device *hdev, struct hid_input *hi)
 		break;
 	}
 
-	if (suffix) {
-		name = devm_kzalloc(&hi->input->dev,
-				    strlen(hdev->name) + strlen(suffix) + 2,
-				    GFP_KERNEL);
-		if (name) {
-			sprintf(name, "%s %s", hdev->name, suffix);
-			hi->input->name = name;
-		}
-	}
+	if (suffix)
+		hi->input->name = devm_kasprintf(&hdev->dev, GFP_KERNEL,
+						 "%s %s", hdev->name, suffix);
 
 	return 0;
 }
-- 
2.40.1