linux-kernel - [PATCH 3.16 019/136] USB: adutux: fix NULL-derefs on disconnect

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Message-ID: <lsq.1576543535.907728721@decadent.org.uk>
Date:   Tue, 17 Dec 2019 00:45:53 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Johan Hovold" <johan@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 019/136] USB: adutux: fix NULL-derefs on disconnect

3.16.80-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@...nel.org>

commit b2fa7baee744fde746c17bc1860b9c6f5c2eebb7 upstream.

The driver was using its struct usb_device pointer as an inverted
disconnected flag, but was setting it to NULL before making sure all
completion handlers had run. This could lead to a NULL-pointer
dereference in a number of dev_dbg statements in the completion handlers
which relies on said pointer.

The pointer was also dereferenced unconditionally in a dev_dbg statement
release() something which would lead to a NULL-deref whenever a device
was disconnected before the final character-device close if debugging
was enabled.

Fix this by unconditionally stopping all I/O and preventing
resubmissions by poisoning the interrupt URBs at disconnect and using a
dedicated disconnected flag.

This also makes sure that all I/O has completed by the time the
disconnect callback returns.

Fixes: 1ef37c6047fe ("USB: adutux: remove custom debug macro and module parameter")
Fixes: 66d4bc30d128 ("USB: adutux: remove custom debug macro")
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20190925092913.8608-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/misc/adutux.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/drivers/usb/misc/adutux.c
+++ b/drivers/usb/misc/adutux.c
@@ -80,6 +80,7 @@ struct adu_device {
 	char			serial_number[8];
 
 	int			open_count; /* number of times this port has been opened */
+	unsigned long		disconnected:1;
 
 	char		*read_buffer_primary;
 	int			read_buffer_length;
@@ -121,7 +122,7 @@ static void adu_abort_transfers(struct a
 {
 	unsigned long flags;
 
-	if (dev->udev == NULL)
+	if (dev->disconnected)
 		return;
 
 	/* shutdown transfer */
@@ -244,7 +245,7 @@ static int adu_open(struct inode *inode,
 	}
 
 	dev = usb_get_intfdata(interface);
-	if (!dev || !dev->udev) {
+	if (!dev) {
 		retval = -ENODEV;
 		goto exit_no_device;
 	}
@@ -327,7 +328,7 @@ static int adu_release(struct inode *ino
 	}
 
 	adu_release_internal(dev);
-	if (dev->udev == NULL) {
+	if (dev->disconnected) {
 		/* the device was unplugged before the file was released */
 		if (!dev->open_count)	/* ... and we're the last user */
 			adu_delete(dev);
@@ -356,7 +357,7 @@ static ssize_t adu_read(struct file *fil
 		return -ERESTARTSYS;
 
 	/* verify that the device wasn't unplugged */
-	if (dev->udev == NULL) {
+	if (dev->disconnected) {
 		retval = -ENODEV;
 		pr_err("No device or device unplugged %d\n", retval);
 		goto exit;
@@ -521,7 +522,7 @@ static ssize_t adu_write(struct file *fi
 		goto exit_nolock;
 
 	/* verify that the device wasn't unplugged */
-	if (dev->udev == NULL) {
+	if (dev->disconnected) {
 		retval = -ENODEV;
 		pr_err("No device or device unplugged %d\n", retval);
 		goto exit;
@@ -801,11 +802,14 @@ static void adu_disconnect(struct usb_in
 
 	usb_deregister_dev(interface, &adu_class);
 
+	usb_poison_urb(dev->interrupt_in_urb);
+	usb_poison_urb(dev->interrupt_out_urb);
+
 	mutex_lock(&adutux_mutex);
 	usb_set_intfdata(interface, NULL);
 
 	mutex_lock(&dev->mtx);	/* not interruptible */
-	dev->udev = NULL;	/* poison */
+	dev->disconnected = 1;
 	mutex_unlock(&dev->mtx);
 
 	/* if the device is not opened, then we clean up right now */