linux-kernel - [PATCH] USB: serial: Fix use after free in debug printk

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Message-ID: <7d0481da-5852-4566-9adb-3a8bb74cb159@stanley.mountain>
Date: Thu, 31 Oct 2024 09:59:10 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] USB: serial: Fix use after free in debug printk

The dev_dbg() call dereferences "urb" but it was already freed on the
previous line.  Move the debug output earlier in the function.

Fixes: 984f68683298 ("USB: serial: io_edgeport.c: remove dbg() usage")
Cc: stable@...r.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 drivers/usb/serial/io_edgeport.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index c7d6b5e3f898..b8f1bd41fb24 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -775,7 +775,10 @@ static void edge_bulk_out_cmd_callback(struct urb *urb)
 	atomic_dec(&CmdUrbs);
 	dev_dbg(&urb->dev->dev, "%s - FREE URB %p (outstanding %d)\n",
 		__func__, urb, atomic_read(&CmdUrbs));
-
+	if (status)
+		dev_dbg(&urb->dev->dev,
+			"%s - nonzero write bulk status received: %d\n",
+			__func__, status);
 
 	/* clean up the transfer buffer */
 	kfree(urb->transfer_buffer);
@@ -783,12 +786,8 @@ static void edge_bulk_out_cmd_callback(struct urb *urb)
 	/* Free the command urb */
 	usb_free_urb(urb);
 
-	if (status) {
-		dev_dbg(&urb->dev->dev,
-			"%s - nonzero write bulk status received: %d\n",
-			__func__, status);
+	if (status)
 		return;
-	}
 
 	/* tell the tty driver that something has changed */
 	if (edge_port->open)
-- 
2.45.2