linux-kernel - [PATCH v2] USB: serial: io_edgeport: Fix use after free in debug printk

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Message-ID: <93490900-d2c6-45e6-b008-8d264e4c11b0@stanley.mountain>
Date: Thu, 31 Oct 2024 12:48:30 +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 v2] USB: serial: io_edgeport: Fix use after free in debug
 printk

The "dev_dbg(&urb->dev->dev, ..." which happens after usb_free_urb(urb)
is a use after free of the "urb" pointer.  Store the "dev" pointer at the
start of the function to avoid this issue.

Fixes: 984f68683298 ("USB: serial: io_edgeport.c: remove dbg() usage")
Cc: stable@...r.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v2: Fix the subsystem prefix and use a "dev" pointer.  It brings the
style in line with the rest of the file, and it's more future proof in
case someone adds a new dev_dbg() later.

 drivers/usb/serial/io_edgeport.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index c7d6b5e3f898..28c71d99e857 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -770,11 +770,12 @@ static void edge_bulk_out_data_callback(struct urb *urb)
 static void edge_bulk_out_cmd_callback(struct urb *urb)
 {
 	struct edgeport_port *edge_port = urb->context;
+	struct device *dev = &urb->dev->dev;
 	int status = urb->status;
 
 	atomic_dec(&CmdUrbs);
-	dev_dbg(&urb->dev->dev, "%s - FREE URB %p (outstanding %d)\n",
-		__func__, urb, atomic_read(&CmdUrbs));
+	dev_dbg(dev, "%s - FREE URB %p (outstanding %d)\n", __func__, urb,
+		atomic_read(&CmdUrbs));
 
 
 	/* clean up the transfer buffer */
@@ -784,8 +785,7 @@ static void edge_bulk_out_cmd_callback(struct urb *urb)
 	usb_free_urb(urb);
 
 	if (status) {
-		dev_dbg(&urb->dev->dev,
-			"%s - nonzero write bulk status received: %d\n",
+		dev_dbg(dev, "%s - nonzero write bulk status received: %d\n",
 			__func__, status);
 		return;
 	}
-- 
2.45.2