linux-kernel - [Regression, 2.6.33-rc1->current git] NULL pointer in usb_serial_probe() introduced by the recent kfifo changes

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Message-Id: <200912230251.31568.rjw@sisk.pl>
Date:	Wed, 23 Dec 2009 02:51:31 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Greg KH <greg@...ah.com>
Cc:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stefani Seibold <stefani@...bold.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [Regression, 2.6.33-rc1->current git] NULL pointer in usb_serial_probe() introduced by the recent kfifo changes

Hi,

Something like the patch below is necessary to fix a new NULL pointer deref
in usb_serial_probe() that appeared after the recent kfifo changes (in short,
the kfifo changes modified the semantics of kfifo_alloc() that
usb_serial_probe() reiled on).

Thanks,
Rafael

---
 drivers/usb/serial/usb-serial.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/usb/serial/usb-serial.c
===================================================================
--- linux-2.6.orig/drivers/usb/serial/usb-serial.c
+++ linux-2.6/drivers/usb/serial/usb-serial.c
@@ -595,8 +595,10 @@ static void port_release(struct device *
 	usb_free_urb(port->write_urb);
 	usb_free_urb(port->interrupt_in_urb);
 	usb_free_urb(port->interrupt_out_urb);
-	if (!IS_ERR(port->write_fifo) && port->write_fifo)
+	if (port->write_fifo) {
 		kfifo_free(port->write_fifo);
+		kfree(port->write_fifo);
+	}
 	kfree(port->bulk_in_buffer);
 	kfree(port->bulk_out_buffer);
 	kfree(port->interrupt_in_buffer);
@@ -939,6 +941,12 @@ int usb_serial_probe(struct usb_interfac
 			dev_err(&interface->dev, "No free urbs available\n");
 			goto probe_error;
 		}
+		port->write_fifo = kzalloc(sizeof(struct kfifo), GFP_KERNEL);
+		if (!port->write_fifo) {
+			dev_err(&interface->dev,
+				"Couldn't allocate write_fifo\n");
+			goto probe_error;
+		}
 		if (kfifo_alloc(port->write_fifo, PAGE_SIZE, GFP_KERNEL))
 			goto probe_error;
 		buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
--
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