firmware loader: fix races during loading firmware

This patch fixes two races in loading firmware:

1, FW_STATUS_DONE should be set before waking up the task waitting
on _request_firmware_load, otherwise FW_STATUS_ABORT may be
thought as DONE mistakenly.

2, Inside _request_firmware_load(), there is a small window between
wait_for_completion() and mutex_lock(&fw_lock), and 'echo 1 > loading'
still may happen during the period, so this patch checks FW_STATUS_DONE
to prevent pages' buffer completed from being freed in firmware_loading_store.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 9 deletions

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 1cbefcfd15f7..1915ad821688 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -243,18 +243,21 @@ static ssize_t firmware_loading_store(struct device *dev,
         switch (loading) {
         case 1:
                 /* discarding any previous partial load */
-                for (i = 0; i < fw_priv->nr_pages; i++)
-                        __free_page(fw_priv->pages[i]);
-                kfree(fw_priv->pages);
-                fw_priv->pages = NULL;
-                fw_priv->page_array_size = 0;
-                fw_priv->nr_pages = 0;
-                set_bit(FW_STATUS_LOADING, &fw_priv->status);
+                if (!test_bit(FW_STATUS_DONE, &fw_priv->status)) {
+                        for (i = 0; i < fw_priv->nr_pages; i++)
+                                __free_page(fw_priv->pages[i]);
+                        kfree(fw_priv->pages);
+                        fw_priv->pages = NULL;
+                        fw_priv->page_array_size = 0;
+                        fw_priv->nr_pages = 0;
+                        set_bit(FW_STATUS_LOADING, &fw_priv->status);
+                }
                 break;
         case 0:
                 if (test_bit(FW_STATUS_LOADING, &fw_priv->status)) {
-                        complete(&fw_priv->completion);
+                        set_bit(FW_STATUS_DONE, &fw_priv->status);
                         clear_bit(FW_STATUS_LOADING, &fw_priv->status);
+                        complete(&fw_priv->completion);
                         break;
                 }
                 /* fallthrough */
@@ -557,7 +560,6 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
 
         wait_for_completion(&fw_priv->completion);
 
-        set_bit(FW_STATUS_DONE, &fw_priv->status);
         del_timer_sync(&fw_priv->timeout);
 
         mutex_lock(&fw_lock);