[PATCH] request_firmware(): avoid race conditions

Avoid race occurs when some process have open file descriptor for class
device attributes and already firmware allocated memory are freed.  Don't
allow negative loading timeout.

Signed-off-by: Stanislaw W. Gruszka <stf_xl@wp.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 97fe13f7f07c..652281402c92 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -74,6 +74,8 @@ static ssize_t
 firmware_timeout_store(struct class *class, const char *buf, size_t count)
 {
         loading_timeout = simple_strtol(buf, NULL, 10);
+        if (loading_timeout < 0)
+                loading_timeout = 0;
         return count;
 }
 
@@ -138,6 +140,10 @@ firmware_loading_store(struct class_device *class_dev,
         switch (loading) {
         case 1:
                 down(&fw_lock);
+                if (!fw_priv->fw) {
+                        up(&fw_lock);
+                        break;
+                }
                 vfree(fw_priv->fw->data);
                 fw_priv->fw->data = NULL;
                 fw_priv->fw->size = 0;
@@ -178,7 +184,7 @@ firmware_data_read(struct kobject *kobj,
 
         down(&fw_lock);
         fw = fw_priv->fw;
-        if (test_bit(FW_STATUS_DONE, &fw_priv->status)) {
+        if (!fw || test_bit(FW_STATUS_DONE, &fw_priv->status)) {
                 ret_count = -ENODEV;
                 goto out;
         }
@@ -238,9 +244,10 @@ firmware_data_write(struct kobject *kobj,
 
         if (!capable(CAP_SYS_RAWIO))
                 return -EPERM;
+
         down(&fw_lock);
         fw = fw_priv->fw;
-        if (test_bit(FW_STATUS_DONE, &fw_priv->status)) {
+        if (!fw || test_bit(FW_STATUS_DONE, &fw_priv->status)) {
                 retval = -ENODEV;
                 goto out;
         }
@@ -418,7 +425,7 @@ request_firmware(const struct firmware **firmware_p, const char *name,
 
         fw_priv = class_get_devdata(class_dev);
 
-        if (loading_timeout) {
+        if (loading_timeout > 0) {
                 fw_priv->timeout.expires = jiffies + loading_timeout * HZ;
                 add_timer(&fw_priv->timeout);
         }