4.10-rc3, firmware loading via user space helper crashes if firmware not present

Hi!

If one requests a FW which does not exist in the FS and the user space helper is used then fw_load_abort() will be called twice which leads to NULL-deref.

It will be called once in firmware_loading_store() (handling the -1 case) and then again in _request_firmware_load() because return value from fw_state_wait_timeout() was negative.

I think this is introduced in by f52cc379423d ("firmware: refactor loading status").

The simple fix would be to not "unlink" the buf by fw_load_abort() in firmware_loading_store() and always rely on firmware_loading_store().

------->8------------------------------------

b/drivers/base/firmware_class.c index 4497d263209f..89eb9de81145 100644

@@ -766,7 +770,7 @@ static ssize_t firmware_loading_store(struct device

*dev, dev_err(dev, "%s: unexpected value (%d)\n", __func__, loading);
/* fallthrough */
case -1:
- fw_load_abort(fw_priv);
+ fw_state_aborted(&fw_buf->fw_st);
break;
}
out:

-------8<------------------------------------

Or should we fix up the ret code handling in __fw_state_wait_common()?

Kuba

I got this backwards, I blamed the wrong commit, it's the 5d47ec02c37e ("firmware: Correct handling of fw_state_wait() return value") in fact. It made the assumption that all errors returned from fw_state_wait_timeout() require calling the abort, while in fact abort should only be called if user mode helper didn't do anything (either it timed out or someone hit ^C).

I'm leaning towards this:

------->8------------------------------------

index 4497d263209f..ce142e6b2c72 100644
@@ -1020,7 +1020,7 @@ static int _request_firmware_load(struct firmware_priv *fw_priv,
 	}
 
 	retval = fw_state_wait_timeout(&buf->fw_st, timeout);
-	if (retval < 0) {
+	if (retval == -ETIMEDOUT || retval == -ERESTARTSYS) {
 		mutex_lock(&fw_lock);
 		fw_load_abort(fw_priv);
 		mutex_unlock(&fw_lock);

-------8<------------------------------------

Unless advised otherwise I will submit this officially on Monday :)