linux-kernel - Re: [RFC] Clarification for “undefined behaviour”?

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <e665514b-5a62-4afb-b267-7c320e4872af@web.de>
Date: Wed, 5 Mar 2025 09:40:43 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: Dan Carpenter <dan.carpenter@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 kernel-janitors@...r.kernel.org, freedreno@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org
Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Archit Taneja <architt@...eaurora.org>, Daniel Vetter <daniel@...ll.ch>,
 David Airlie <airlied@...il.com>, Jeykumar Sankaran <jsanka@...eaurora.org>,
 Jordan Crouse <jordan@...micpenguin.net>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
 Simona Vetter <simona@...ll.ch>, Vinod Koul <vkoul@...nel.org>,
 cocci@...ia.fr, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Clarification for “undefined behaviour”?

>>> The address of a data structure member was determined before
>>> a corresponding null pointer check in the implementation of
>>> the functions “dpu_hw_pp_enable_te” and “dpu_hw_pp_get_vsync_info”.
>>>
>>> Thus avoid the risk for undefined behaviour by removing extra
>>> initialisations for the variable “c” (also because it was already
>>> reassigned with the same value behind this pointer check).
> There is no undefined behavior here.

Is there a need to improve the wording precision?

There are words which denote a special meaning according to aspects of
the programming language “C”.
https://en.cppreference.com/w/c/language/behavior

Dereferences of null pointers are treated in special ways.
The system might be configurable to collaborate also with data accesses
together with the address “zero”.
Would you like to distinguish supported software functionality any further?

Regards,
Markus