linux-kernel - Re: [PATCH 1/1] s390/dasd: fix string length handling

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: <ZO0k1Par4i4FBCWF@google.com>
Date:   Mon, 28 Aug 2023 15:51:00 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     'Heiko Carstens' <hca@...ux.ibm.com>, Jens Axboe <axboe@...nel.dk>,
        Stefan Haberland <sth@...ux.ibm.com>,
        Jan Höppner <hoeppner@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 1/1] s390/dasd: fix string length handling

On Mon, Aug 28, 2023 at 05:18:37PM +0000, David Laight wrote:
> From: Heiko Carstens
> > Sent: 28 August 2023 16:32
> >  	if (strlen(uid.vduit) > 0)
> 
> Does the compiler know enough to optimise that brain-dead test?
> 

For the purposes of skipping diagnostics, no; clang performs semantic
analysis BEFORE optimization (which is handled by LLVM). As such, clang
will produce diagnostics on dead code.

Partly because LLVM isn't very ergonomic at emitting diagnostics from
the backend, partly because Clang code owner and developers don't want
clang to emit diagnostics dependent on optimization level.

I disagree with my compatriots, and you can read more thoughts here:
https://discourse.llvm.org/t/rfc-improving-clangs-middle-and-back-end-diagnostics/69261?u=nickdesaulniers