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AJvYcCU+RlgSQVkqIA0sZ4WgIYVrzSkWWFA9YzGdO0UgIuzyeOpJmrt1cenfI9sYyo2oCQgYPSqAYvuzv2xbgIRnWMTrZ9A= X-Gm-Message-State: AOJu0YwLSwGsct9dmu0ruLp5cJATX+sDm9l1WliEQSP9XN3pqxJdUOBL ub5a8ClNI6laAP80HbMeFlLw3Fuw8OS6PztgQAGg4JdVMYjVOeqxpSNP3WrVj8x5cV5U4DzUZQx GAIvR61uuj2qVibfccOiV6OvfnP5c8kPMP+vU X-Google-Smtp-Source: AGHT+IHFX6BLG6gStI5mGJe8kD5iHHOGF4/Un66b6V0pmO7shQqI26eQsamvdYGJ3CG+Ua8RPpXvkMXqkHnDAqYCv7M= X-Received: by 2002:a05:6214:4a86:b0:6ab:710a:d84a with SMTP id 6a1803df08f44-6abc3e88e06mr16373676d6.23.1716539326544; Fri, 24 May 2024 01:28:46 -0700 (PDT) MIME-Version: 1.0 References: <20240523215029.4160518-1-bjohannesmeyer@gmail.com> In-Reply-To: <20240523215029.4160518-1-bjohannesmeyer@gmail.com> From: Alexander Potapenko Date: Fri, 24 May 2024 10:28:05 +0200 Message-ID: Subject: Re: [PATCH] x86: kmsan: Fix hook for unaligned accesses To: Brian Johannesmeyer Cc: Marco Elver , Dmitry Vyukov , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: 98ci1yapdfqpaotrm9dtqkjg3hjywxae X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 9643140011 X-HE-Tag: 1716539327-866131 X-HE-Meta: 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 ZFXzLUxT lw140cVu/Y11YMJ2fB/p2lBJZYyI1ygE130/OefneVk8rSaMZQlvd0AgXjzmhOMJ1THgD0c7x0F6kb6r2Zv12N6EB4evWozM0EQlKWLjtJs7gx2vpA6YX9Kxm+U+/qcQEd++qVPZnxlYhNtnfFIR9shFTaldmsCdpeEr+RvKKmibIZUE5GTWQWMX2FFuL6ymd/vFii+fcwh+6lzSJ0UlsBMOFZqCvuxAt1TTpvAZ78+MXf4+Cp1wsatwgW8/NqpTlDXJN+XS54Z2ObiVMLPswiTGhTQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, May 23, 2024 at 11:50=E2=80=AFPM Brian Johannesmeyer wrote: > > When called with a 'from' that is not 4-byte-aligned, > string_memcpy_fromio() calls the movs() macro to copy the first few bytes= , > so that 'from' becomes 4-byte-aligned before calling rep_movs(). This > movs() macro modifies 'to', and the subsequent line modifies 'n'. > > As a result, on unaligned accesses, kmsan_unpoison_memory() uses the > updated (aligned) values of 'to' and 'n'. Hence, it does not unpoison the > entire region. > > This patch saves the original values of 'to' and 'n', and passes those to > kmsan_unpoison_memory(), so that the entire region is unpoisoned. Nice catch! Does it fix any known bugs? > Signed-off-by: Brian Johannesmeyer Reviewed-by: Alexander Potapenko