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Subject[RFC PATCH 02/13] driver core: firmware loader: fix races during loading firmware
Date
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>
---
drivers/base/firmware_class.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index f789bbd..6e96b8c 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 */
@@ -552,7 +555,6 @@ 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);
--
1.7.9.5


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