Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933504Ab3CVKQj (ORCPT ); Fri, 22 Mar 2013 06:16:39 -0400 Received: from cyclops.biessmann.org ([134.0.25.77]:37480 "EHLO cyclops.biessmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754016Ab3CVKQi (ORCPT ); Fri, 22 Mar 2013 06:16:38 -0400 X-Greylist: delayed 375 seconds by postgrey-1.27 at vger.kernel.org; Fri, 22 Mar 2013 06:16:38 EDT 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 , stable@vger.kernel.org Subject: [PATCH] register_console: prevent adding the same console twice Date: Fri, 22 Mar 2013 11:10:52 +0100 Message-Id: <1363947052-15605-1-git-send-email-andreas@biessmann.de> X-Mailer: git-send-email 1.7.10.4 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: 1490 Lines: 48 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. 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: stable@vger.kernel.org --- kernel/printk.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/printk.c b/kernel/printk.c index 0b31715..f78bfcd 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -2254,6 +2254,14 @@ void register_console(struct console *newcon) unsigned long flags; struct console *bcon = NULL; + if (console_drivers) + for_each_console(bcon) + if (bcon == newcon) { + pr_warn("prevent adding console '%s%d' twice\n", + newcon->name, newcon->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/