Driver core fix for 3.10-rc7

Here's a single patch for the firmware core that resolves a reported
 oops in the firmware core that people have been hitting.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core fix from Greg Kroah-Hartman:
 "Here's a single patch for the firmware core that resolves a reported
  oops in the firmware core that people have been hitting."

* tag 'driver-core-3.10-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  firmware loader: fix use-after-free by double abort

drivers/base/firmware_class.c

@@ -450,8 +450,18 @@ static void fw_load_abort(struct firmware_priv *fw_priv)
 {
 	struct firmware_buf *buf = fw_priv->buf;
 
+	/*
+	 * There is a small window in which user can write to 'loading'
+	 * between loading done and disappearance of 'loading'
+	 */
+	if (test_bit(FW_STATUS_DONE, &buf->status))
+		return;
+
 	set_bit(FW_STATUS_ABORT, &buf->status);
 	complete_all(&buf->completion);
+
+	/* avoid user action after loading abort */
+	fw_priv->buf = NULL;
 }
 
 #define is_fw_load_aborted(buf)	\
@@ -528,7 +538,12 @@ static ssize_t firmware_loading_show(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
 	struct firmware_priv *fw_priv = to_firmware_priv(dev);
-	int loading = test_bit(FW_STATUS_LOADING, &fw_priv->buf->status);
+	int loading = 0;
+
+	mutex_lock(&fw_lock);
+	if (fw_priv->buf)
+		loading = test_bit(FW_STATUS_LOADING, &fw_priv->buf->status);
+	mutex_unlock(&fw_lock);
 
 	return sprintf(buf, "%d\n", loading);
 }
@@ -570,12 +585,12 @@ static ssize_t firmware_loading_store(struct device *dev,
 				      const char *buf, size_t count)
 {
 	struct firmware_priv *fw_priv = to_firmware_priv(dev);
-	struct firmware_buf *fw_buf = fw_priv->buf;
+	struct firmware_buf *fw_buf;
 	int loading = simple_strtol(buf, NULL, 10);
 	int i;
 
 	mutex_lock(&fw_lock);
-
+	fw_buf = fw_priv->buf;
 	if (!fw_buf)
 		goto out;
 
@@ -777,10 +792,6 @@ static void firmware_class_timeout_work(struct work_struct *work)
 			struct firmware_priv, timeout_work.work);
 
 	mutex_lock(&fw_lock);
-	if (test_bit(FW_STATUS_DONE, &(fw_priv->buf->status))) {
-		mutex_unlock(&fw_lock);
-		return;
-	}
 	fw_load_abort(fw_priv);
 	mutex_unlock(&fw_lock);
 }
@@ -861,8 +872,6 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
 
 	cancel_delayed_work_sync(&fw_priv->timeout_work);
 
-	fw_priv->buf = NULL;
-
 	device_remove_file(f_dev, &dev_attr_loading);
 err_del_bin_attr:
 	device_remove_bin_file(f_dev, &firmware_attr_data);