Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755528Ab3CYI6p (ORCPT ); Mon, 25 Mar 2013 04:58:45 -0400 Received: from cyclops.biessmann.org ([134.0.25.77]:42579 "EHLO cyclops.biessmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750760Ab3CYI6o (ORCPT ); Mon, 25 Mar 2013 04:58:44 -0400 From: =?UTF-8?q?Andreas=20Bie=C3=9Fmann?= To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Andreas=20Bie=C3=9Fmann?= , Greg Kroah-Hartman , Kay Sievers , Ben Hutchings , stable@kernel.org Subject: [PATCH v2] register_console: prevent adding the same console twice Date: Mon, 25 Mar 2013 09:59:24 +0100 Message-Id: <1364201964-2990-1-git-send-email-andreas@biessmann.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1363947052-15605-1-git-send-email-andreas@biessmann.de> 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 Content-Length: 1704 Lines: 54 This patch guards the console_drivers list to be corrupted. The for_each_console() macro insist on a strictly forward list ended by NULL: con0->next->con1->next->NULL Without this patch it may happen easily to destroy this list for example by adding 'earlyprintk' twice, especially on embedded devices where the early console is often a single static instance. This will result in the following list: con0->next->con0 This in turn will result in an endless loop in console_unlock() later on by printing the first __log_buf line endlessly. Signed-off-by: Andreas Bießmann Cc: Greg Kroah-Hartman Cc: Kay Sievers Cc: Ben Hutchings Cc: stable@kernel.org --- since v1: * use WARN() as Ben suggested * print 'already registered' instead of 'prevent registering' kernel/printk.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/printk.c b/kernel/printk.c index abbdd9e..180ee25 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -2214,6 +2214,13 @@ void register_console(struct console *newcon) unsigned long flags; struct console *bcon = NULL; + if (console_drivers) + for_each_console(bcon) + if (WARN(bcon == newcon, + "console '%s%d' already registered\n", + bcon->name, bcon->index)) + return; + /* * before we register a new CON_BOOT console, make sure we don't * already have a valid console -- 1.7.10.4 -- 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/