From nobody Tue Dec 16 18:29:17 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 19911304BC6 for ; Thu, 11 Dec 2025 10:43:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765449842; cv=none; b=G5sZTu2h5pqAkeFR5DRmcGCl/PrTg9x7Sy1BSi8F5OXciDQdmKrcTCKmIPjaikE+f55xGs979k/Cz+PtnXz4LHe1yEOvzxqwzDT+57XZGvc9cokRNI/eCe4Ez/rr/Glgu8WRljO+6+HhXYm3hP6g8Y7a43R6fmGxwh0xcVjriho= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765449842; c=relaxed/simple; bh=Rsfmd7zbC+kSZ3iat7Z+yufKodHJKLHaalHhwgTU+L8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=J2JUKd9FXdBqtrswM2yDY+XLmZuR5S3bVZj1rT3WlsKF2EErxEpJR+ACVnmyzuf+bdwLEs46+lZ9ZWWM95o9dPWz7W2VDT1aAyJckIHCz3gVdPTuCMLca8qRA3K9RCi2Q3U7T2MkViCdcuCO3XwR6A6jwzGwLBTeMb6g6dAH3fw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HBoVWUbI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HBoVWUbI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7B94C4CEF7; Thu, 11 Dec 2025 10:43:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765449839; bh=Rsfmd7zbC+kSZ3iat7Z+yufKodHJKLHaalHhwgTU+L8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HBoVWUbIPjgDrlY7e+sbBXcwhv9wyvl/oGC9FVjnkNVQbmXNcvHpSiizWHBTWgmVu 676b5JCo+l/vhSxnZkG5ex76Egqqm4ujKFANztBXWD/69rPUxapQR+jv7fWXfH8rMO 7bBSCRPpnBWxr7QFRqPeSuCaQv+kuC1EXcei63Z0N4r0T8q7IsyF1cdxJAqLa79re/ 6S1wWL9Ofd/CVmAMEIKMEM+TCjSxJjn6f5/0o4BDhkIWCohnLcMd/e72uqPy92Txqp TeaIWji2IswH2f6gsDWEVp+tHgksXSMZekCWKawCfVxLWFHlpm2TNBjIjHsJkH5rVD CRfGfp2igqIcw== Date: Thu, 11 Dec 2025 11:43:54 +0100 From: Alejandro Colomar To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Alejandro Colomar , Kees Cook , Christopher Bazley , Rasmus Villemoes , Marco Elver , Michal Hocko , Linus Torvalds , Al Viro , Alexander Potapenko , Dmitry Vyukov , Jann Horn , Andrew Morton , "Maciej W. Rozycki" Subject: [PATCH v6 2/4] mm: Fix benign off-by-one bugs Message-ID: <9c38dd009c17b0219889c7089d9bdde5aaf28a8e.1765449750.git.alx@kernel.org> X-Mailer: git-send-email 2.51.0 References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Acked-by: Marco Elver Cc: Kees Cook Cc: Christopher Bazley Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Alexander Potapenko Cc: Jann Horn Cc: Andrew Morton Cc: Linus Torvalds Cc: Rasmus Villemoes Cc: Marco Elver Cc: Michal Hocko Cc: Al Viro Signed-off-by: Alejandro Colomar Message-ID: <515445ae064d4b8599899bf0d8b480dadd2ff843.1752182685.git.alx@ke= rnel.org> --- mm/kfence/kfence_test.c | 4 ++-- mm/kmsan/kmsan_test.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c index 00034e37bc9f..5725a367246d 100644 --- a/mm/kfence/kfence_test.c +++ b/mm/kfence/kfence_test.c @@ -110,7 +110,7 @@ static bool report_matches(const struct expect_report *= r) =20 /* Title */ cur =3D expect[0]; - end =3D &expect[0][sizeof(expect[0]) - 1]; + end =3D ARRAY_END(expect[0]); switch (r->type) { case KFENCE_ERROR_OOB: cur +=3D scnprintf(cur, end - cur, "BUG: KFENCE: out-of-bounds %s", @@ -140,7 +140,7 @@ static bool report_matches(const struct expect_report *= r) =20 /* Access information */ cur =3D expect[1]; - end =3D &expect[1][sizeof(expect[1]) - 1]; + end =3D ARRAY_END(expect[1]); =20 switch (r->type) { case KFENCE_ERROR_OOB: diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c index 902ec48b1e3e..b5ad5dfb2c00 100644 --- a/mm/kmsan/kmsan_test.c +++ b/mm/kmsan/kmsan_test.c @@ -105,7 +105,7 @@ static bool report_matches(const struct expect_report *= r) =20 /* Title */ cur =3D expected_header; - end =3D &expected_header[sizeof(expected_header) - 1]; + end =3D ARRAY_END(expected_header); =20 cur +=3D scnprintf(cur, end - cur, "BUG: KMSAN: %s", r->error_type); =20 --=20 2.51.0