linux-kernel - [PATCH] cdc-acm: fix race between initial clearing halt and open

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Message-ID: <20250717141259.2345605-1-oneukum@suse.com>
Date: Thu, 17 Jul 2025 16:12:50 +0200
From: Oliver Neukum <oneukum@...e.com>
To: gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Oliver Neukum <oneukum@...e.com>
Subject: [PATCH] cdc-acm: fix race between initial clearing halt and open

On the devices that need their endpoints to get an
initial clear_halt, this needs to be done before
the devices can be opened. That means it needs to be
before the devices are registered.

Fixes: 15bf722e6f6c0 ("cdc-acm: Add support of ATOL FPrint fiscal printers")
Signed-off-by: Oliver Neukum <oneukum@...e.com>
---
 drivers/usb/class/cdc-acm.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index c2ecfa3c8349..5a334e370f4d 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1520,6 +1520,12 @@ static int acm_probe(struct usb_interface *intf,
 			goto err_remove_files;
 	}
 
+	if (quirks & CLEAR_HALT_CONDITIONS) {
+		/* errors intentionally ignored */
+		usb_clear_halt(usb_dev, acm->in);
+		usb_clear_halt(usb_dev, acm->out);
+	}
+
 	tty_dev = tty_port_register_device(&acm->port, acm_tty_driver, minor,
 			&control_interface->dev);
 	if (IS_ERR(tty_dev)) {
@@ -1527,11 +1533,6 @@ static int acm_probe(struct usb_interface *intf,
 		goto err_release_data_interface;
 	}
 
-	if (quirks & CLEAR_HALT_CONDITIONS) {
-		usb_clear_halt(usb_dev, acm->in);
-		usb_clear_halt(usb_dev, acm->out);
-	}
-
 	dev_info(&intf->dev, "ttyACM%d: USB ACM device\n", minor);
 
 	return 0;
-- 
2.50.1