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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702043792; x=1702648592; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=SlUqBCSJE7b+NOWHxQNrRwEhp2gTAvY03mAPrdADOdo=; b=ksXzvn0XcY2ug57pnJ/OFILywvdWLrcmQEOTO4tVhZGcFGSXGb7wVbUE3Q5lFvz/ix XR+x5AV9LzEmoKQ00A6uLK2DqOYj5b/I1Mj8f/Q8rdgwuLUkEBl39uqSGP2l/3IQm26N 2RG0qdwR3Bnkwf5MldnKt/WB5zp4xqnLLI/uVkCml8opctk6e68dthFp2A2jZiD7SNgq vP53FxTGVEzH6k4WEoxbbwHxTr8waR63rMGAalBpP1Si+DUb5PjtxWuhkh5diB9eKcrF P1DXe9PuJBz6xWaxR5mOwj41SnIN7Dhczspmqhso/9t9xAOybxVcXmVFD26PdEr2ooUw EhiA== X-Gm-Message-State: AOJu0YxtJdEsQtSExVtSrXkuMV+lU/7XaCtLYCBV0LKHxy0MyO0OHXZl BqXgC9uOyU7zr5xKEoJ0PAamYa9SDhnYwmxCqfrRCA== X-Received: by 2002:a05:6214:5802:b0:67a:a951:7fc2 with SMTP id mk2-20020a056214580200b0067aa9517fc2mr4258051qvb.119.1702043792410; Fri, 08 Dec 2023 05:56:32 -0800 (PST) MIME-Version: 1.0 References: <20231121220155.1217090-1-iii@linux.ibm.com> <20231121220155.1217090-18-iii@linux.ibm.com> In-Reply-To: From: Alexander Potapenko Date: Fri, 8 Dec 2023 14:55:56 +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-Spam-Status: No, score=-8.4 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Fri, 08 Dec 2023 05:56:42 -0800 (PST) On Fri, Dec 8, 2023 at 1:53=E2=80=AFPM Alexander Potapenko wrote: > > 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 and even Tested-by: Alexander Potapenko