greybus: loopback: make sure to list_del on connection_exit

gb_loopback_connection_exit does a kfree on a data structure associated
with a loopback connection but fails to do a corresponding list_del(). On
subsequent enumerations this can lead to a NULL pointer dereference. Each
list_add in gb_loopback_connection_init() must have a corresponding
list_del in gb_loopback_connection_exit(), this patch adds the relevant
list_del() and ensures that an appropriate mutex protecting gb_dev.list is
held while doing so.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reported-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c
index 8dd648c..231d1d4 100644 (file)
--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -944,18 +944,23 @@ static void gb_loopback_connection_exit(struct gb_connection *connection)
        struct gb_loopback *gb = connection->private;
        struct kobject *kobj = &connection->bundle->intf->module->dev.kobj;
 
-       gb_dev.count--;
-       connection->private = NULL;
        if (!IS_ERR_OR_NULL(gb->task))
                kthread_stop(gb->task);
 
+       mutex_lock(&gb_dev.mutex);
+
+       connection->private = NULL;
        kfifo_free(&gb->kfifo_lat);
        kfifo_free(&gb->kfifo_ts);
        if (!gb_dev.count)
                sysfs_remove_groups(kobj, loopback_dev_groups);
        sysfs_remove_groups(&connection->dev.kobj, loopback_con_groups);
        debugfs_remove(gb->file);
+       list_del(&gb->entry);
        kfree(gb);
+       gb_dev.count--;
+
+       mutex_unlock(&gb_dev.mutex);
 }
 
 static struct gb_protocol loopback_protocol = {