Input: keyboard - fix lack of locking when traversing handler->h_list
Keyboard handler should not attempt to traverse handler->h_list on
its own, without any locking, otherwise it races with registering
and unregistering of input handles which leads to crashes.
Introduce input_handler_for_each_handle() helper that allows safely
iterate over all handles attached to a particular handler and switch
keyboard handler to use it.
Reported-by: Jim Paradis <jparadis@redhat.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/input.c b/drivers/input/input.c
index cc763c9..5d6421b 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1651,6 +1651,38 @@
EXPORT_SYMBOL(input_unregister_handler);
/**
+ * input_handler_for_each_handle - handle iterator
+ * @handler: input handler to iterate
+ * @data: data for the callback
+ * @fn: function to be called for each handle
+ *
+ * Iterate over @bus's list of devices, and call @fn for each, passing
+ * it @data and stop when @fn returns a non-zero value. The function is
+ * using RCU to traverse the list and therefore may be usind in atonic
+ * contexts. The @fn callback is invoked from RCU critical section and
+ * thus must not sleep.
+ */
+int input_handler_for_each_handle(struct input_handler *handler, void *data,
+ int (*fn)(struct input_handle *, void *))
+{
+ struct input_handle *handle;
+ int retval = 0;
+
+ rcu_read_lock();
+
+ list_for_each_entry_rcu(handle, &handler->h_list, h_node) {
+ retval = fn(handle, data);
+ if (retval)
+ break;
+ }
+
+ rcu_read_unlock();
+
+ return retval;
+}
+EXPORT_SYMBOL(input_handler_for_each_handle);
+
+/**
* input_register_handle - register a new input handle
* @handle: handle to register
*
@@ -1683,7 +1715,7 @@
* we can't be racing with input_unregister_handle()
* and so separate lock is not needed here.
*/
- list_add_tail(&handle->h_node, &handler->h_list);
+ list_add_tail_rcu(&handle->h_node, &handler->h_list);
if (handler->start)
handler->start(handle);
@@ -1706,7 +1738,7 @@
{
struct input_dev *dev = handle->dev;
- list_del_init(&handle->h_node);
+ list_del_rcu(&handle->h_node);
/*
* Take dev->mutex to prevent race with input_release_device().
@@ -1714,6 +1746,7 @@
mutex_lock(&dev->mutex);
list_del_rcu(&handle->d_node);
mutex_unlock(&dev->mutex);
+
synchronize_rcu();
}
EXPORT_SYMBOL(input_unregister_handle);