Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934663AbbKSSjb (ORCPT ); Thu, 19 Nov 2015 13:39:31 -0500 Received: from michel.telenet-ops.be ([195.130.137.88]:49279 "EHLO michel.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934603AbbKSSjG (ORCPT ); Thu, 19 Nov 2015 13:39:06 -0500 From: Geert Uytterhoeven To: Greg Kroah-Hartman , Simon Horman , Magnus Damm , Yoshinori Sato , Laurent Pinchart Cc: linux-serial@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH 09/25] serial: sh-sci: Avoid overflow in sci_baud_calc_hscif() Date: Thu, 19 Nov 2015 19:38:48 +0100 Message-Id: <1447958344-836-10-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1447958344-836-1-git-send-email-geert+renesas@glider.be> References: <1447958344-836-1-git-send-email-geert+renesas@glider.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2004 Lines: 52 If bps >= 1048576, the multiplication of "(sr * (1 << (2 * c + 1))" and "bps" will overflow, and both br and err will contain bogus values. Skip the current and all higher clock select predividers when overflow is detected. Simplify the calculations using intermediates while we're at it. Signed-off-by: Geert Uytterhoeven --- drivers/tty/serial/sh-sci.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index fba1e1eea15dc3a1..97a0f8ef5adc55a2 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1870,7 +1870,7 @@ static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps, static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr, unsigned int *srr, unsigned int *cks) { - unsigned int sr, br, c; + unsigned int sr, br, a, b, c; int err, recv_margin; int min_err = 1000; /* 100% */ int recv_max_margin = 0; @@ -1880,12 +1880,14 @@ static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr, for (sr = 8; sr <= 32; sr++) { for (c = 0; c <= 3; c++) { /* integerized formulas from HSCIF documentation */ - br = DIV_ROUND_CLOSEST(freq, (sr * - (1 << (2 * c + 1)) * bps)); + a = sr * (1 << (2 * c + 1)); + if (bps > UINT_MAX / a) + break; + + b = a * bps; + br = DIV_ROUND_CLOSEST(freq, b); br = clamp(br, 1U, 256U); - err = DIV_ROUND_CLOSEST(freq, (br * bps * sr * - (1 << (2 * c + 1)) / 1000)) - - 1000; + err = DIV_ROUND_CLOSEST(freq, (br * b) / 1000) - 1000; /* Calc recv margin * M: Receive margin (%) * N: Ratio of bit rate to clock (N = sampling rate) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/