From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S970722AbdI0A0f (ORCPT ); Tue, 26 Sep 2017 20:26:35 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43002 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964956AbdI0A0e (ORCPT ); Tue, 26 Sep 2017 20:26:34 -0400 Date: Tue, 26 Sep 2017 17:26:32 -0700 From: Andrew Morton To: Minchan Kim Cc: Sergey Senozhatsky , linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: Re: [PATCH] zsmalloc: calling zs_map_object() from irq is a bug Message-Id: <20170926172632.cf302deff749d12f74d8a4da@linux-foundation.org> In-Reply-To: <20170920064739.GA11000@bbox> References: <20170920063941.14662-1-sergey.senozhatsky@gmail.com> <20170920064739.GA11000@bbox> 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 Wed, 20 Sep 2017 15:47:39 +0900 Minchan Kim wrote: > On Wed, Sep 20, 2017 at 03:39:41PM +0900, Sergey Senozhatsky wrote: > > Use BUG_ON(in_interrupt()) in zs_map_object(). Calling this > > function from IRQ is a bug, because we use per-CPU mappings > > and interrupt may corrupt those buffers. > > > > Signed-off-by: Sergey Senozhatsky > > IMHO, corruption the buffer would be not enough to be a BUG_ON > which stop the system fully so user loses any chances to shut > down smooth/hunt it down. > > More serious thing of our case is that it can leak other user's > data by overwriting, which is more concern I am thinking now. > In an off-list email Linus has basically stated that all new uses of BUG_ON should include words in the changelog or code comments explaining why it is justifiable to kill the machine when the condition triggers. So can we please have a v2 with the appropriate comment?