linux-kernel - Re: [PATCH 1/1] misc: Prevent double registration and deregistration of miscdevice

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Message-ID: <2025082631-hypnotist-snazzy-147a@gregkh>
Date: Tue, 26 Aug 2025 12:40:45 +0200
From: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To: Xion Wang (王鑫) <Xion.Wang@...iatek.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	wsd_upstream <wsd_upstream@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Huadian Liu (刘华典) <huadian.liu@...iatek.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"arnd@...db.de" <arnd@...db.de>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 1/1] misc: Prevent double registration and deregistration
 of miscdevice

On Tue, Aug 26, 2025 at 07:58:47AM +0000, Xion Wang (王鑫) wrote:
> > Again, this shouldn't be something that any driver should hit as this
> > usage is not in the kernel tree that I can see.  Attempting to
> > re-register a device multiple times is normally never a good idea.
> 
> Thank you for your comments.
> 
> I am not the owner of the WiFi driver and do not have full details of
> its internal logic. However, during internal integration and stress
> testing, we observed an issue where repeated registration and
> deregistration of a misc device by the WiFi module led to corruption of
> the misc_list. While I cannot provide the exact reasoning behind the
> WiFi driver's design, I wanted to report the problem and share our
> findings with the community in case similar patterns exist elsewhere,
> including in vendor or out-of-tree drivers.

We do not "harden" our internal apis for external drivers, we fix
drivers to not do foolish things :)

Please fix your out-of-tree code, it should not be even touching the
miscdev api, as that is not something a wifi driver should be
interacting with.  Please use the correct one instead, and then you will
not have this type of issue.

thanks,

greg k-h