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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>
This commit is contained in:
Ming Lei 2012-08-04 12:01:17 +08:00 committed by Greg Kroah-Hartman
parent 65710cb6ea
commit 28eefa750b
1 changed files with 11 additions and 9 deletions
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20
drivers/base/firmware_class.c
View File

@ -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);