linux-kernel - Re: [PATCH] driver core: faux: fix Undefined Behavior in faux_device

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Message-ID: <2025061446-wriggle-modulator-f7f3@gregkh>
Date: Sat, 14 Jun 2025 07:53:22 -0400
From: Greg KH <gregkh@...uxfoundation.org>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Benjamin.Cheatham@....com, Jonathan.Cameron@...wei.com, dakr@...nel.org,
	dan.j.williams@...el.com, linux-acpi@...r.kernel.org,
	linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	marc.herbert@...ux.intel.com, rafael.j.wysocki@...el.com,
	rafael@...nel.org, sudeep.holla@....com,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Kees Cook <kees@...nel.org>
Subject: Re: [PATCH] driver core: faux: fix Undefined Behavior in
 faux_device_destroy()

On Sat, Jun 14, 2025 at 12:50:37PM +0200, Miguel Ojeda wrote:
> On Fri, 13 Jun 2025 20:33:42 -0400 Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > Great writeup, but as Miguel says, this isn't needed at all, the kernel
> > relies on the compiler to be sane :)
> 
> We may still want to clean them up, e.g. for tooling -- Kees/Dan: do we?
> e.g. I see a similar case with discussion at:
> 
>     https://lore.kernel.org/lkml/3f1e7aaa-501a-44f1-8122-28e9efa0a33c@web.de/
> 
> Which in the end was picked up as commit 2df2c0caaecf ("fbdev: au1100fb:
> Move a variable assignment behind a null pointer check").

If "tooling" trips over stuff like this, then we should fix the tooling
as again, the kernel relies on this not being "optimized away" by the
compiler in many places.

thanks,

greg k-h