linux-kernel - Re: [PATCH] hwmon/coretemp: Simplify platform device antics

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <563f0162-ae94-0d74-bb25-1c0753af9329@leemhuis.info>
Date:   Tue, 15 Nov 2022 11:14:36 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Robin Murphy <robin.murphy@....com>, fenghua.yu@...el.com,
        jdelvare@...e.com, linux@...ck-us.net
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux.dev, janusz.krzysztofik@...ux.intel.com,
        lucas.demarchi@...el.com
Subject: Re: [PATCH] hwmon/coretemp: Simplify platform device antics

On 10.11.22 17:20, Robin Murphy wrote:
> Coretemp's vestigial platform driver is odd. All the real work is done
> globally by the initcall and CPU hotplug notifiers, while the "driver"
> effectively just wraps an allocation and the registration of the hwmon
> interface in a long-winded round-trip through the driver core. The whole
> logic of dynamically creating and destroying platform devices to bring
> the interfaces up and down is fatally flawed right away, since it
> assumes platform_device_add() will synchronously bind the driver and set
> drvdata before it returns, thus results in a NULL dereference if
> drivers_autoprobe is turned off for the platform bus. Furthermore, the
> unusual approach of doing that from within a CPU hotplug notifier is
> also problematic. It's already commented in the code that it deadlocks
> suspend, but it also causes lockdep issues for other drivers or
> subsystems which may want to legitimately register a CPU hotplug
> notifier from a platform bus notifier.
> 
> All of these issues can be solved by ripping this questionable behaviour
> out completely, simply tying the platform devices to the lifetime of the
> module itself, and directly managing the hwmon interfaces from the
> hotplug notifiers. There is a slight user-visible change in that
> /sys/bus/platform/drivers/coretemp will no longer appear, and
> /sys/devices/platform/coretemp.n will remain present if package n is
> hotplugged off, but hwmon users should really only be looking for the
> presence of the hwmon interfaces, whose behaviour remains unchanged.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

For future archeologists and the regression tracking this afaics should
have the following tags, as outlined by the documentation[1].

Link:
https://lore.kernel.org/lkml/20220922101036.87457-1-janusz.krzysztofik@linux.intel.com/
Link: https://gitlab.freedesktop.org/drm/intel/issues/6641

Any maybe a reported-by for Janusz, too.

Ciao, Thorsten

[1] see Documentation/process/submitting-patches.rst
(http://docs.kernel.org/process/submitting-patches.html) and
Documentation/process/5.Posting.rst
(https://docs.kernel.org/process/5.Posting.html)

P.S.:

#regzbot ^backmonitor:
https://lore.kernel.org/lkml/20220922101036.87457-1-janusz.krzysztofik@linux.intel.com/