staging: usbip: fix the usage of kthread_stop()

stub_shutdown_connection() and vhci_shutdown_connection() use
task_is_dead() before kthread_stop(). This buys nothing and wrong.
kthread_stop() is fine even if this thread is dead. However, if it
is dead nothing protects this task_struct, we shouldn't touch this
memory.

Change the code to do the necessary get_task_struct/put_task_struct.

This patch assumes that

	- xxx_shutdown_connection() is always called, so we can't
	  leak the task_struct.

	- kthread_stop_put() can't be called twice on the same task.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Matt Mooney <mfm@muteddisk.com>,
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/staging/usbip/usbip_common.h b/drivers/staging/usbip/usbip_common.h
index c7b888ca54f5..5d89c0fd6f7b 100644
--- a/drivers/staging/usbip/usbip_common.h
+++ b/drivers/staging/usbip/usbip_common.h
@@ -292,6 +292,23 @@ struct usbip_device {
 	} eh_ops;
 };
 
+#define kthread_get_run(threadfn, data, namefmt, ...)			   \
+({									   \
+	struct task_struct *__k						   \
+		= kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \
+	if (!IS_ERR(__k)) {						   \
+		get_task_struct(__k);					   \
+		wake_up_process(__k);					   \
+	}								   \
+	__k;								   \
+})
+
+#define kthread_stop_put(k)		\
+	do {				\
+		kthread_stop(k);	\
+		put_task_struct(k);	\
+	} while (0)
+
 /* usbip_common.c */
 void usbip_dump_urb(struct urb *purb);
 void usbip_dump_header(struct usbip_header *pdu);