[PATCH 0/3] USB: usb-skeleton: regression fix

[PATCH 0/3] USB: usb-skeleton: regression fix

[Johan Hovold]

I messed up when submitting the runtime PM fixes last week and failed to
notice that the change to usb-skeleton depended on another fix I already
had in my tree (I did notice the conflict, but rebased and sent a v2
also without the prerequisite patch).

So here's a regression fix to a commit in usb-linus for usb-skeleton. :/

Included are also a use-after-free fix and a related clean up.

Johan


Johan Hovold (3):
  USB: usb-skeleton: fix NULL-deref on disconnect
  USB: usb-skeleton: fix use-after-free after driver unbind
  USB: usb-skeleton: drop redundant in-urb check

 drivers/usb/usb-skeleton.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

-- 
2.23.0

[PATCH 1/3] USB: usb-skeleton: fix NULL-deref on disconnect

[Johan Hovold]

The driver was using its struct usb_interface pointer as an inverted
disconnected flag and was setting it to NULL before making sure all
completion handlers had run. This could lead to NULL-pointer
dereferences in the dev_err() statements in the completion handlers
which relies on said pointer.

Fix this by using a dedicated disconnected flag.

Note that this is also addresses a NULL-pointer dereference at release()
and a struct usb_interface reference leak introduced by a recent runtime
PM fix, which depends on and should have been submitted together with
this patch.

Fixes: 4212cd74ca6f ("USB: usb-skeleton.c: remove err() usage")
Fixes: 5c290a5e42c3 ("USB: usb-skeleton: fix runtime PM after driver unbind")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/usb-skeleton.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 8001d6384c73..c2843fcfa52d 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -61,6 +61,7 @@ struct usb_skel {
 	spinlock_t		err_lock;		/* lock for errors */
 	struct kref		kref;
 	struct mutex		io_mutex;		/* synchronize I/O with disconnect */
+	unsigned long		disconnected:1;
 	wait_queue_head_t	bulk_in_wait;		/* to wait for an ongoing read */
 };
 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
@@ -238,7 +239,7 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count,
 	if (rv < 0)
 		return rv;
 
-	if (!dev->interface) {		/* disconnect() was called */
+	if (dev->disconnected) {		/* disconnect() was called */
 		rv = -ENODEV;
 		goto exit;
 	}
@@ -420,7 +421,7 @@ static ssize_t skel_write(struct file *file, const char *user_buffer,
 
 	/* this lock makes sure we don't submit URBs to gone devices */
 	mutex_lock(&dev->io_mutex);
-	if (!dev->interface) {		/* disconnect() was called */
+	if (dev->disconnected) {		/* disconnect() was called */
 		mutex_unlock(&dev->io_mutex);
 		retval = -ENODEV;
 		goto error;
@@ -571,7 +572,7 @@ static void skel_disconnect(struct usb_interface *interface)
 
 	/* prevent more I/O from starting */
 	mutex_lock(&dev->io_mutex);
-	dev->interface = NULL;
+	dev->disconnected = 1;
 	mutex_unlock(&dev->io_mutex);
 
 	usb_kill_anchored_urbs(&dev->submitted);
-- 
2.23.0

[PATCH 2/3] USB: usb-skeleton: fix use-after-free after driver unbind

[Johan Hovold]

The driver failed to stop its read URB on disconnect, something which
could lead to a use-after-free in the completion handler after driver
unbind in case the character device has been closed.

Fixes: e7389cc9a7ff ("USB: skel_read really sucks royally")
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/usb-skeleton.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index c2843fcfa52d..be311787403e 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -575,6 +575,7 @@ static void skel_disconnect(struct usb_interface *interface)
 	dev->disconnected = 1;
 	mutex_unlock(&dev->io_mutex);
 
+	usb_kill_urb(dev->bulk_in_urb);
 	usb_kill_anchored_urbs(&dev->submitted);
 
 	/* decrement our usage count */
-- 
2.23.0

[PATCH 3/3] USB: usb-skeleton: drop redundant in-urb check

[Johan Hovold]

The driver bails out at probe if we can't find a bulk-in endpoint or
if we fail to allocate the URB, so drop the check in read().

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/usb-skeleton.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index be311787403e..2dc58766273a 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -230,8 +230,7 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count,
 
 	dev = file->private_data;
 
-	/* if we cannot read at all, return EOF */
-	if (!dev->bulk_in_urb || !count)
+	if (!count)
 		return 0;
 
 	/* no concurrent readers */
-- 
2.23.0