From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941270AbcKNDUQ (ORCPT ); Sun, 13 Nov 2016 22:20:16 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45173 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753929AbcKNCFg (ORCPT ); Sun, 13 Nov 2016 21:05:36 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Gregor Boirie" , "Jonathan Cameron" , "Lars-Peter Clausen" Date: Mon, 14 Nov 2016 00:14:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 252/346] iio:core: fix IIO_VAL_FRACTIONAL sign handling In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.39-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Gregor Boirie commit 171c0091837c81ed5c949fec6966bb5afff2d1cf upstream. 7985e7c100 ("iio: Introduce a new fractional value type") introduced a new IIO_VAL_FRACTIONAL value type meant to represent rational type numbers expressed by a numerator and denominator combination. Formating of IIO_VAL_FRACTIONAL values relies upon do_div() usage. This fails handling negative values properly since parameters are reevaluated as unsigned values. Fix this by using div_s64_rem() instead. Computed integer part will carry properly signed value. Formatted fractional part will always be positive. Fixes: 7985e7c100 ("iio: Introduce a new fractional value type") Signed-off-by: Gregor Boirie Reviewed-by: Lars-Peter Clausen Signed-off-by: Jonathan Cameron Signed-off-by: Ben Hutchings --- drivers/iio/industrialio-core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -404,9 +404,8 @@ ssize_t iio_format_value(char *buf, unsi return sprintf(buf, "%d.%09u\n", vals[0], vals[1]); case IIO_VAL_FRACTIONAL: tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]); - vals[1] = do_div(tmp, 1000000000LL); - vals[0] = tmp; - return sprintf(buf, "%d.%09u\n", vals[0], vals[1]); + vals[0] = (int)div_s64_rem(tmp, 1000000000, &vals[1]); + return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1])); case IIO_VAL_FRACTIONAL_LOG2: tmp = (s64)vals[0] * 1000000000LL >> vals[1]; vals[1] = do_div(tmp, 1000000000LL);