linux-kernel - Re: PROBLEM: NULL pointer dereference in dell_set

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Message-ID: <20180204162954.GA24841@localhost.localdomain>
Date:   Sun, 4 Feb 2018 19:29:54 +0300
From:   Alexander Sergeyev <sergeev917@...il.com>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Mario.Limonciello@...l.com, dvhart@...radead.org,
        andy@...radead.org, linux-kernel@...r.kernel.org,
        mjg59@...f.ucam.org, platform-driver-x86@...r.kernel.org
Subject: Re: PROBLEM: NULL pointer dereference in dell_set_arguments() in 4.15

>To make dell_micmute_led_set() work properly we need to ensure that either WMI 
>or SMM driver is already loaded and initialized.

>From the looks of the call trace dell_micmute_led_set() is called from device 
phase of initialization. Which means that there is a use of dell-laptop 
interface while the module is not initialized (since late_initcall). 
Previously, this led to crashes.

But dell_micmute_led_set() does not touch the module state now, so nothing is 
technically broken; dell-smbios and dell-smbios-smm use subsys_initcall, so 
they are ready. But WMI driver is in the same phase with intel hda, so there 
might be something there.