linux-kernel - Re: [PATCH v2 18/33] lib/string: Add KMSAN support to strlcpy() and strlcat()

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Message-ID: <679e7142d4ed4da34b6b4b756216170d6c789e84.camel@linux.ibm.com>
Date:   Wed, 13 Dec 2023 01:53:51 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: [PATCH v2 18/33] lib/string: Add KMSAN support to strlcpy() and
 strlcat()

On Fri, 2023-12-08 at 17:50 +0100, Alexander Potapenko wrote:
> On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <iii@...ux.ibm.com>
> wrote:
> > 
> > Currently KMSAN does not fully propagate metadata in strlcpy() and
> > strlcat(), because they are built with -ffreestanding and call
> > memcpy(). In this combination memcpy() calls are not instrumented.
> 
> Is this something specific to s390?

Nice catch - I can't reproduce this behavior anymore. Even if I go
back to the clang version that first introduced KMSAN on s390x, the
memset() instrumentation with -ffreestanding is still there. I should
have written down more detailed notes after investigating this, but
here we are. I will drop this patch as well as 10/33.

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