From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29126C8303C for ; Mon, 7 Jul 2025 14:42:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 980328D0002; Mon, 7 Jul 2025 10:42:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 930C76B0102; Mon, 7 Jul 2025 10:42:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 846C28D0002; Mon, 7 Jul 2025 10:42:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 7532C6B00FF for ; Mon, 7 Jul 2025 10:42:49 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 2C56E1A00E0 for ; Mon, 7 Jul 2025 14:42:49 +0000 (UTC) X-FDA: 83637735258.03.EA3C2CD Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf01.hostedemail.com (Postfix) with ESMTP id 7D4E240002 for ; Mon, 7 Jul 2025 14:42:47 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=V4OaCflZ; spf=pass (imf01.hostedemail.com: domain of alx@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=alx@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1751899367; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1A+i7aMcf5ReW7LkDyYrEnwRq+3f66ir16xsIi4HmOM=; b=bXz/nfMhpgang0u438g6hc+42xi8XaWAxY9h/HOF1AzG4g58FH40d8TQzkuOgl0QPp3Ld7 /WaaKkVX7nkprUHRGNJL3eflIYj+OsOfpkWuIqT93RIdvIePXtInrNP8AFAJdG9G1uu+za 9rpNWIK/UREDLuYXO3cXEy51MpuPJHQ= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=V4OaCflZ; spf=pass (imf01.hostedemail.com: domain of alx@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=alx@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1751899367; a=rsa-sha256; cv=none; b=TsvRnm3LI0ay4up6NV1uzJv/otMWCAQsLQXgcIsYZI9kuRPFu6vb+667GbJDyTSbBraCvz kH5/q31PwO4P5I1QVL8OLbda1Ot9Lylarp5s2el3pjjkBB7Mj3uAtvx4NZ/D7AiyxlZLVJ oSg4oxN4GMhQq2wsQBPvPRL/p6NbPPM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id AFD755C5462; Mon, 7 Jul 2025 14:42:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DCBDC4CEE3; Mon, 7 Jul 2025 14:42:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751899366; bh=MDzuMRrp2AXCWKZWYbBsCLTTjaSYUNv6L3J0WLWh/vQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=V4OaCflZjkEO5qWNNtTxP65kPvUz4/hSXVxXXK2dYGHyENjl8f0zGFt6YNIAgsQqe yYsDzE5XADCTX73JfOJrydbNoJyD0mdpxcFFi68fDTEwioDZ1ByKpSR6Yu5fMI98zy hX8aY4MlK6F0kbNd2j8bRL2GFV5Wk9CyW9rNFz62BCd8w24QJZXGSNoz12uDC1fUUf EINc4QmLSd/MpU2QGCSeCHulaU05uY5kIHh0Rmi1lpmLyNgkHT6mAi4Jw0gLiL6aXW 4r2EbSTE9u0Z7RFm1NORCO7DavMvrLtqVWWL9YaVjEhJ4vYBk/TtXPiV4VfaCtZ68p ZIYRajREJivIA== Date: Mon, 7 Jul 2025 16:42:43 +0200 From: Alejandro Colomar To: Michal Hocko Cc: Marco Elver , 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: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="tmiwotmrfmdi6oyz" Content-Disposition: inline In-Reply-To: X-Stat-Signature: q4sb8u7o7pr3q15bymcem3hi9t9a815g X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7D4E240002 X-HE-Tag: 1751899367-616013 X-HE-Meta: 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 Vz/K+nkS 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 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: --tmiwotmrfmdi6oyz Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable From: Alejandro Colomar To: Michal Hocko Cc: Marco Elver , 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 References: <740755c1a888ae27de3f127c27bf925a91e9b264.1751862634.git.alx@kernel.org> MIME-Version: 1.0 In-Reply-To: Hi Michal, On Mon, Jul 07, 2025 at 09:53:31AM +0200, Michal Hocko wrote: > 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") > >=20 > > 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. >=20 > 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. For the dead code, I can remove the fixes tags, and even the changes themselves, since there are good reasons to keep the dead code (consistency, and avoiding a future programmer forgetting to add it back when adding a subsequent seprintf() call). For the fixes to UB, do you prefer the Fixes tags to be removed too? Have a lovely day! Alex > --=20 > Michal Hocko > SUSE Labs --=20 --tmiwotmrfmdi6oyz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEES7Jt9u9GbmlWADAi64mZXMKQwqkFAmhr3OMACgkQ64mZXMKQ wqmhQhAAs+ekX9398aALI01OsOZ18qRcUwUGAgNGOEKzODVWKq+ZfCv5kpLjB8Rx mz7WZld1t7roGUyTkEE6qInFFtJ9EB2Oc0WqZCBNEHvS7hRiWLbJdaYv3vdT5hl6 ++tJ/HhXTGChathW1i4KfKiu5iZdre5B0h36dXQJvU70Xewnca8uY7Vq4u4mfpwU POUiVLo1FPMx5PfJYILFFMhI8PRWrAwx6wlkbjHBmVaRqG4z286j4FonO8wwwwNt 8E8KmyNt2a8wsc0+ezpmDJ7lgsWpxr3qTp3FGIby9yokzHBUrc4IAlzj9agSPmlT qWLcFUwdFPzKb4bQCX2zVfjidlbO14g6iS71wINotWZvKhy8e9Wtza78qUFhpGV4 77u0tXXT1dVd3K2P0HYz8AmXtgawUDUA/8DAF25SxfHIodsdJq35OsSGPzfrbIfC BuT+K4OhfWoODvzcOYFpEyrz2a+YgXRep4GfRDc69PrGhmQk8S68V9vcMft/tzvy k+ggvc9f1Y1Y1MtXFKV91pGhD5//TnJA1UYduI/HOz+2DeTFk+s62nHjiy/zXdzE fvsiLzgRkXT8geMyrGRtKxnKKWqWEXrt0kmfr8h6FwjrBjL3hRzsrCCSyqCgmKyJ isD88CxA4o8wntqCuOxhMtsOVK5jXG6pN56W+eZ/LOfzfz1MSRE= =mTHU -----END PGP SIGNATURE----- --tmiwotmrfmdi6oyz--