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Fri, 08 Dec 2023 04:54:23 -0800 (PST) MIME-Version: 1.0 References: <20231121220155.1217090-1-iii@linux.ibm.com> <20231121220155.1217090-18-iii@linux.ibm.com> In-Reply-To: <20231121220155.1217090-18-iii@linux.ibm.com> From: Alexander Potapenko Date: Fri, 8 Dec 2023 13:53:41 +0100 Message-ID: Subject: Re: [PATCH v2 17/33] mm: kfence: Disable KMSAN when checking the canary To: Ilya Leoshkevich Cc: Alexander Gordeev , Andrew Morton , Christoph Lameter , David Rientjes , Heiko Carstens , Joonsoo Kim , Marco Elver , Masami Hiramatsu , Pekka Enberg , Steven Rostedt , Vasily Gorbik , Vlastimil Babka , Christian Borntraeger , Dmitry Vyukov , Hyeonggon Yoo <42.hyeyoo@gmail.com>, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Mark Rutland , Roman Gushchin , Sven Schnelle Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 11F35C0009 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 14txawyk6tch7kxho1t9utufdfud1c5j X-HE-Tag: 1702040064-633617 X-HE-Meta: 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 +ucKWca5 nht3isxMm/7pd/Col9nRyQpIRyoWqom4wLirsP7vKdJK+abof3pECTufntG+BUm4EUcunHbYSuyR2SsEu56b7s1soHHgIFx5JZAh3FmbGbcocNNpvUa+sek4mzS/JEVrISQ+UoGaVc+LgL5E8sUuuwyQqjbWwngusZC9aVi1aDrGi/PBunUoxdIM7t/MAh4z4wY4FjuP0pPBr+llf9k7kr4NpF2lG+2+6TqW0GymhnRvGkoeSaW+5zxSCef7OkPltK5dN2Jo2yQfb0rhNRMs5+yznTQLtQFX1T6ptQAiziHeAFanfYVN5pCVpERwTYdWah904sCd0+kzZL3FmhDzQ0iwmol7BUE28cBKU X-Bogosity: Ham, tests=bogofilter, spamicity=0.401622, 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 Tue, Nov 21, 2023 at 11:02=E2=80=AFPM Ilya Leoshkevich wrote: > > KMSAN warns about check_canary() accessing the canary. > > The reason is that, even though set_canary() is properly instrumented > and sets shadow, slub explicitly poisons the canary's address range > afterwards. > > Unpoisoning the canary is not the right thing to do: only > check_canary() is supposed to ever touch it. Instead, disable KMSAN > checks around canary read accesses. > > Signed-off-by: Ilya Leoshkevich Reviewed-by: Alexander Potapenko