Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760718AbaLLGd1 (ORCPT ); Fri, 12 Dec 2014 01:33:27 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51947 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759328AbaLLGQ6 (ORCPT ); Fri, 12 Dec 2014 01:16:58 -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, "Peter Hurley" , "Robert =?UTF-8?Q?=C5=9Awi=C4=99cki?=" , "Greg Kroah-Hartman" Date: Fri, 12 Dec 2014 06:14:25 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 116/164] serial: Fix divide-by-zero fault in uart_get_divisor() In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:c97:8151:cc89:c28d 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 3.2.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley 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: Ben Hutchings --- drivers/tty/serial/serial_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -360,7 +360,7 @@ uart_get_baud_rate(struct uart_port *por * The spd_hi, spd_vhi, spd_shi, spd_warp kludge... * Die! Die! Die! */ - if (baud == 38400) + if (try == 0 && baud == 38400) baud = altbaud; /* -- 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/