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

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Date:   Fri, 13 Jan 2017 13:32:58 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Daniel Wagner <daniel.wagner@...-carit.de>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: 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------------------------------------

diff --git a/drivers/base/firmware_class.c
b/drivers/base/firmware_class.c index 4497d263209f..89eb9de81145 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -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