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[109.81.17.167]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-454a998a731sm131477575e9.17.2025.07.07.00.53.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Jul 2025 00:53:32 -0700 (PDT) Date: Mon, 7 Jul 2025 09:53:31 +0200 From: Michal Hocko To: Marco Elver Cc: Alejandro Colomar , linux-mm@kvack.org, linux-hardening@vger.kernel.org, Kees Cook , Christopher Bazley , shadow <~hallyn/shadow@lists.sr.ht>, linux-kernel@vger.kernel.org, Andrew Morton , kasan-dev@googlegroups.com, Dmitry Vyukov , Alexander Potapenko , Christoph Lameter , David Rientjes , Vlastimil Babka , Roman Gushchin , Harry Yoo , Andrew Clayton , Jann Horn , Linus Torvalds Subject: Re: [RFC v3 5/7] mm: Fix benign off-by-one bugs Message-ID: References: <740755c1a888ae27de3f127c27bf925a91e9b264.1751862634.git.alx@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2EBEB80007 X-Stat-Signature: c6acub6sfisbs36fbzmqd5kt7dr1ajsu X-HE-Tag: 1751874813-241451 X-HE-Meta: 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 EmFheC83 m1dF+q8y3MV26iR0oJSVHw8HVHBzOWsaz+Bf1J2i9e+DU4o252KzknYoOAcwez6Cbd2a16ImFQxLbNs94TNsV1dU9QRWRO3CQubZTLfK3Q+TGKyba/LDlx6W6xf9OM/MyWR85EABzDKJb7obAYYqgGleIMg4kz+9sO2buixBFrxkJiAj/vNjVFhgRpqcrX4i9My8RwAhCSpwnw0pLfreZtBr7fChHE2HxNlU7KqXBj70ZdZS+LBbkPqjqula/GiWZBWCN2M4ev5Sw1U1Jr88EkdZPvqovVahiOQT1Y2Zg1c8Mge/gPBUr50YjyhJ4bQ9AahLOT2DO3fYoy1duhR2f56CxfEUYo9qDx9VR/95HEtUUOaci33T4L4RwhQ31qYm4Xm2ZTfNH0tt4zmES6t3B5wBKFLkAOCquIrJ+ 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 Mon 07-07-25 09:46:12, Marco Elver wrote: > On Mon, 7 Jul 2025 at 07:06, Alejandro Colomar wrote: > > > > We were wasting a byte due to an off-by-one bug. s[c]nprintf() > > doesn't write more than $2 bytes including the null byte, so trying to > > pass 'size-1' there is wasting one byte. Now that we use seprintf(), > > the situation isn't different: seprintf() will stop writing *before* > > 'end' --that is, at most the terminating null byte will be written at > > 'end-1'--. > > > > Fixes: bc8fbc5f305a (2021-02-26; "kfence: add test suite") > > Fixes: 8ed691b02ade (2022-10-03; "kmsan: add tests for KMSAN") > > Not sure about the Fixes - this means it's likely going to be > backported to stable kernels, which is not appropriate. There's no > functional problem, and these are tests only, so not worth the churn. As long as there is no actual bug fixed then I believe those Fixes tags are more confusing than actually helpful. And that applies to other patches in this series as well. -- Michal Hocko SUSE Labs