From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D7643371897 for ; Tue, 14 Jul 2026 02:09:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783994953; cv=none; b=YQIsZz0oqN/shkC288SowvQSAwE5B9/IhLT8SscnyB8LVw6T9kqSPalY8aWPSW7EBJA8u+QsFGIvqUMH4d/Q0BroSZlBXMJFxodKlnUwezHB/SlchRUP4HG28WHUIaVO68Zj5/uzvfVxHNHHcz/Rvj+gF7HX4+7Kcl5vmPOz8Zw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783994953; c=relaxed/simple; bh=5yHMTWRWbULPlrw5ASNfCsCaILwpG3e7hITKNK+LCw0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MxdSQ75A3g9YV3aCjr20EEZn/DdIUzd5dnH3MTHXFxBQU3AT3xxh2ZlKv0FN1FltY2LKGj8P7cYktevdGkhYI9IB2S2JrrmrNP41vJLcMkumrsVW88SnBG/VGkUrH3aF1pkadWj6exvcwlg9XTBDBhbDPlJcZD9sqVhCr5Z7I1A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H8u9BD0A; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="H8u9BD0A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 208D01F00A3E; Tue, 14 Jul 2026 02:09:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783994951; bh=pETjYaZMGko3hrO+Jgu0Q4kja+K+bIP8i1GGytGwMbM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=H8u9BD0ANPyvxHfW1b3n8lvHijUMCobTzDeS2nGwELNoGFZxs+cJFFRkkmT31hJmw lRtNpE3hE7NifsHwToxB54sBEmyIsWrkLt5U/G87xvq79IX93PBZhH5hJJtzRaaFoe dpjlQNzFBPBuTH+1VHk/pn9UnBJL0jP8EWO9rlrpRpr50Cisct4BBEMFEPTMcWddUD dYFisRm/Gt0CZYFC/bvHKAoW15f9GtuiWa9QngSj63bsI9M3o/Jo/JW09IzsGvzfwA +8BYeet3o+aw9anwqLjD6+Qz4yXm8qcd7/G/v9srKt8EbCvrBDjOi+6oSEruSu2FY3 5tqw5cpBB5HHg== From: Sasha Levin To: stable@vger.kernel.org Cc: Herman van Hazendonk , Andy Shevchenko , Jonathan Cameron , Sasha Levin Subject: [PATCH 5.15.y 2/2] iio: common: st_sensors: honour channel endianness in read_axis_data Date: Mon, 13 Jul 2026 22:09:08 -0400 Message-ID: <20260714020908.2355876-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260714020908.2355876-1-sashal@kernel.org> References: <2026071350-armored-aspirin-5d78@gregkh> <20260714020908.2355876-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Herman van Hazendonk [ Upstream commit 55052184ac9011db2ea983e54d6c21f0b1079a12 ] st_sensors_read_axis_data() unconditionally decoded multi-byte results with get_unaligned_le16() / get_unaligned_le24() regardless of the channel's declared scan_type.endianness. For every ST sensor that has used this helper since it was introduced this happened to be fine because the ST IMU/accel/gyro/pressure families publish their data registers as little-endian and the channel specs in those drivers declare IIO_LE accordingly. The LSM303DLH magnetometer however publishes its X/Y/Z output as a pair of big-endian bytes (the H register sits at the lower address, 0x03/0x05/0x07, and the L register immediately after), and its channel specs in st_magn_core.c correctly declare IIO_BE -- but read_axis_data() ignored that and decoded as little-endian, swapping the high and low bytes of every magnetometer sample. The LSM303DLHC and LSM303DLM share the same st_magn_16bit_channels (IIO_BE) and were therefore byte-swapped by the same bug; users of those parts will see different in_magn_*_raw values after this fix lands. The bug is most visible on a stationary chip: in earth's field the true X reading is small and the high byte sits at 0x00, so swapping the bytes pins sysfs X at exactly the low byte's pattern (e.g. 0x00F0 = 240). Y and Z still appear "to vary" because their magnitudes are larger and the noise in the low byte produces big swings in the swapped high byte: before (LSM303DLH flat, sysfs in_magn_*_raw): X=240 (stuck), Y= 12032..23296, Z=-16128..-9728 after (direct i2c-dev big-endian decode, same chip same orientation): X≈-4096, Y≈210, Z≈80 (sensible values reflecting earth's ambient field at low gauss range) Fix read_axis_data() to dispatch on ch->scan_type.endianness and call get_unaligned_be16() / get_unaligned_be24() when the channel declares IIO_BE. Existing IIO_LE consumers (st_accel, st_gyro, st_pressure, st_lsm6dsx and others) are unaffected because their channel specs already declare IIO_LE and the LE path is unchanged. While restructuring the branches, replace the previously implicit silent-success-with-uninitialised-*data fall-through for byte_for_channel outside 1..3 with an explicit return -EINVAL. No in-tree ST sensor publishes such a channel, but the new behaviour is strictly safer than handing userspace garbage. Fixes: 23491b513bcd ("iio:common: Add STMicroelectronics common library") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-7 sparse smatch clang-analyzer coccinelle checkpatch Assisted-by: Sashiko:claude-opus-4-7 Signed-off-by: Herman van Hazendonk Reviewed-by: Andy Shevchenko Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin --- .../iio/common/st_sensors/st_sensors_core.c | 23 ++++++++++++++----- 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c index aff981551617e8..309d8d78e21ad0 100644 --- a/drivers/iio/common/st_sensors/st_sensors_core.c +++ b/drivers/iio/common/st_sensors/st_sensors_core.c @@ -528,6 +528,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev, u8 *outdata; struct st_sensor_data *sdata = iio_priv(indio_dev); unsigned int byte_for_channel; + u32 tmp; byte_for_channel = DIV_ROUND_UP(ch->scan_type.realbits + ch->scan_type.shift, 8); @@ -540,12 +541,22 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev, if (err < 0) goto st_sensors_free_memory; - if (byte_for_channel == 1) - *data = (s8)*outdata; - else if (byte_for_channel == 2) - *data = (s16)get_unaligned_le16(outdata); - else if (byte_for_channel == 3) - *data = (s32)sign_extend32(get_unaligned_le24(outdata), 23); + if (byte_for_channel == 1) { + tmp = *outdata; + } else if (byte_for_channel == 2) { + if (ch->scan_type.endianness == IIO_BE) + tmp = get_unaligned_be16(outdata); + else + tmp = get_unaligned_le16(outdata); + } else if (byte_for_channel == 3) { + if (ch->scan_type.endianness == IIO_BE) + tmp = get_unaligned_be24(outdata); + else + tmp = get_unaligned_le24(outdata); + } else { + return -EINVAL; + } + *data = sign_extend32(tmp, BYTES_TO_BITS(byte_for_channel) - 1); st_sensors_free_memory: kfree(outdata); -- 2.53.0