From nobody Thu Oct 2 02:05:17 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 B977D265CA8 for ; Thu, 25 Sep 2025 13:20:51 +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=1758806451; cv=none; b=hvar5J+c1hpAEaxqjSenlmkD4UC27tKhGdZGL7q0AONzjF4wR7Mxd1iD4sK1VkHcpPY2wliMusMBILxe8oUYgEriDd0ciF16kNqIpAFiWv2S9Z1KA7hJcNvGZC0gJXFBH74GLXCWq27y+fMsRym0rYQgRsb+3o0lfq0cYgqvUJo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758806451; c=relaxed/simple; bh=4d3Ij8ruJRTlJEB94A/a0pL/HtNqz2IJeGpX2wtPsV8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QH+9lCss9D6dlzJkt4DLEVL5J9JToS/GU+9cMWVA/YgBEO7muIkeTUY4YdebaVipWbJ4XzjkHGNhK7BwRgRW31F3/lvsvV9mRcujjiw4hyZUbO/VxKoAtQCIxMHZluzPnwuQZGNmNpvv4ywTqOwOPenorj5hjspig5GvXSaKAi0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GVkXhoEX; 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="GVkXhoEX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BD4BC113D0; Thu, 25 Sep 2025 13:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758806451; bh=4d3Ij8ruJRTlJEB94A/a0pL/HtNqz2IJeGpX2wtPsV8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GVkXhoEXilKkOjTEb8ioW/Yzsw8YCM8wbejZfFApnpoimIs16eqUtGSN1SPSxQMN2 6QeS0zS9PRkwfA+3frQKjXZ5qAjKjmi+RaEj5T3uaUvNGeGT+7kpuOMNTmu239E5A1 6fNzhqonp3msszrEadp78MI4LynybCvsP8nEANCQFLLjifKN3bHiiyspA79z4jek5u ieTFjiiEjhNEBcpJ7iEpxu0wAB9/lDuyFa6+84ACWPdMEZmPI/brRlbHwzp/AmHGfm kPRToyy+U9/gm45DkW38Xq1gjbFSIUj79ZeMtXemYqtFODYikwO//nHAF1S6uTwsiy KFn6ms/O1gOSw== Date: Thu, 25 Sep 2025 15:20:44 +0200 From: Alejandro Colomar To: linux-kernel@vger.kernel.org Cc: Alejandro Colomar , Marco Elver , Kees Cook , Christopher Bazley , Alexander Potapenko , Dmitry Vyukov , Jann Horn , Andrew Morton , Linus Torvalds , Rasmus Villemoes , Michal Hocko , Al Viro Subject: [PATCH v1 2/3] mm: Fix benign off-by-one bugs Message-ID: <87445e701574058b142e036c3b8a0f505086ab64.1758806023.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..1ad81e6b27ea 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 ENDOF(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 ENDOF(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 c6c5b2bbede0..758405d8b7a7 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 ENDOF(expected_header); =20 cur +=3D scnprintf(cur, end - cur, "BUG: KMSAN: %s", r->error_type); =20 --=20 2.51.0