linux-kernel - [PATCH 0/2] s390/fpu: Fix kmsan false-positive report

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Message-ID: <20251106160845.1334274-2-aleksei.nikiforov@linux.ibm.com>
Date: Thu,  6 Nov 2025 17:08:44 +0100
From: Aleksei Nikiforov <aleksei.nikiforov@...ux.ibm.com>
To: Alexander Potapenko <glider@...gle.com>
Cc: Marco Elver <elver@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Thomas Huth <thuth@...hat.com>,
        Juergen Christ <jchrist@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Aleksei Nikiforov <aleksei.nikiforov@...ux.ibm.com>
Subject: [PATCH 0/2] s390/fpu: Fix kmsan false-positive report

A false-positive kmsan report is detected when running ping command.

An inline assembly instruction 'vstl' can write varied amount of bytes
depending on value of one of arguments. clang generates kmsan write helper
call depending on inline assembly constraints. Constraints are evaluated
compile-time, but value of argument is known only at runtime.

Due to this, clang cannot generate kmsan write helper call with correct
size and a kmsan helper is implemented and called to correct this and
remove false-positive report.

Aleksei Nikiforov (2):
  instrumented.h: Add function instrument_write_after
  s390/fpu: Fix kmsan in fpu_vstl function

 arch/s390/include/asm/fpu-insn.h |  2 ++
 include/linux/instrumented.h     | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

-- 
2.43.7