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

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Message-ID: <4d54e4f6-0d98-4b42-9bea-169f3b8772bb@sabinyo.mountain>
Date: Wed, 25 Jun 2025 10:21:24 -0500
From: Dan Carpenter <dan.carpenter@...aro.org>
To: marc.herbert@...ux.intel.com
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Dan Williams <dan.j.williams@...el.com>, rafael.j.wysocki@...el.com,
	linux-cxl@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Ben Cheatham <Benjamin.Cheatham@....com>,
	Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH] driver core: faux: fix Undefined Behavior in
 faux_device_destroy()

On Fri, Jun 13, 2025 at 07:15:56PM +0000, marc.herbert@...ux.intel.com wrote:
> gcc -O0: Segmentation fault (core dumped)
> gcc -O1: ptr is zero
> gcc -O2: ptr is NOT zero!!!
> gcc -O3: ptr is NOT zero!!!
> gcc -Og: ptr is zero

Btw, this is testing dereferences where the kernel code is doing pointer
math.  No one disagrees about dereferences after a check.

regards,
dan carpenter