From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965388AbbA1Eho (ORCPT ); Tue, 27 Jan 2015 23:37:44 -0500 Received: from mail.kernel.org ([198.145.29.136]:40889 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965167AbbA1EYz (ORCPT ); Tue, 27 Jan 2015 23:24:55 -0500 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Hurley , Greg Kroah-Hartman , Zefan Li Subject: [PATCH 3.4 139/177] serial: Fix divide-by-zero fault in uart_get_divisor() Date: Wed, 28 Jan 2015 12:09:57 +0800 Message-Id: <1422418236-12852-230-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Hurley 3.4.106-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 547039ec502076e60034eeb79611df3433a99b7d upstream. uart_get_baud_rate() will return baud == 0 if the max rate is set to the "magic" 38400 rate and the SPD_* flags are also specified. On the first iteration, if the current baud rate is higher than the max, the baud rate is clamped at the max (which in the degenerate case is 38400). On the second iteration, the now-"magic" 38400 baud rate selects the possibly higher alternate baud rate indicated by the SPD_* flag. Since only two loop iterations are performed, the loop is exited, a kernel WARNING is generated and a baud rate of 0 is returned. Reproducible with: setserial /dev/ttyS0 spd_hi base_baud 38400 Only perform the "magic" 38400 -> SPD_* baud transform on the first loop iteration, which prevents the degenerate case from recognizing the clamped baud rate as the "magic" 38400 value. Reported-by: Robert Święcki Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zefan Li --- drivers/tty/serial/serial_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 4185cc5..82aac29 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -355,7 +355,7 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios, * The spd_hi, spd_vhi, spd_shi, spd_warp kludge... * Die! Die! Die! */ - if (baud == 38400) + if (try == 0 && baud == 38400) baud = altbaud; /* -- 1.9.1