[PATCH 4.14 094/186] HID: multitouch: Correct devm device reference for hidinput input_dev name

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rahul Rameshbabu <sergeantsagara@protonmail.com>

[ Upstream commit 4794394635293a3e74591351fff469cea7ad15a2 ]

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>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20230824061308.222021-3-sergeantsagara@protonmail.com
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 0fa3bd2b035e7..55b1023af31fa 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1136,7 +1136,6 @@ static void mt_post_parse(struct mt_device *td)
 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 hid_field *field = hi->report->field[0];
 	int ret;
@@ -1196,15 +1195,9 @@ static int mt_input_configured(struct hid_device *hdev, struct hid_input *hi)
 		}
 	}
 
-	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