From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755899AbbAPUYH (ORCPT ); Fri, 16 Jan 2015 15:24:07 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46850 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751886AbbAPUYG (ORCPT ); Fri, 16 Jan 2015 15:24:06 -0500 Date: Fri, 16 Jan 2015 12:24:04 -0800 From: Andrew Morton To: Johannes Weiner Cc: Rasmus Villemoes , linux-kernel@vger.kernel.org Subject: Re: Issue with 'lib/vsprintf.c: don't try to fix pointer wrap-around' Message-Id: <20150116122404.e82eb86b5c46afdd0d00df1d@linux-foundation.org> In-Reply-To: <20150116162357.GA10859@phnom.home.cmpxchg.org> References: <20150116162357.GA10859@phnom.home.cmpxchg.org> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 16 Jan 2015 11:23:57 -0500 Johannes Weiner wrote: > Hi Rasmus, > > I have trouble booting my test machine with this patch in -mm: > > commit bb2e066c6943e62e9650bb129f416dacf138f8b1 > Author: Rasmus Villemoes > Date: Wed Jan 14 01:00:44 2015 +0000 > > lib/vsprintf.c: don't try to fix pointer wrap-around > > Actual kernel buffers can't wrap into the user address space. If someone > manages to pass a buf/size combination that wraps, it is most likely due > to a bug in the caller. Instead of trying to fix it by using a smaller > part of the buffer, bail out. > > Signed-off-by: Rasmus Villemoes > Cc: Jiri Kosina > Cc: Randy Dunlap > Signed-off-by: Andrew Morton > > After I get "Loading bzImage-new... ok" from the bootloader, the > serial console remains quiet. > > A WARN_ON_ONCE() inside vsnprintf() looks like it would deadlock > instantly when triggering this overflow from printk(), no? Dammit, I was starting at that printk, ended up deciding it was OK, didn't think about deadlocks. logbuf_lock and recursion_bug, for a start... I'll drop the patch. I assume all this means that your machine is trying to trigger that warning condition? I wonder what the call site is.