From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 723CDC3A59F for ; Mon, 26 Aug 2019 13:29:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C90D2053B for ; Mon, 26 Aug 2019 13:29:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566826166; bh=B8w4oTKAlSq8ZbOEvl/7t4CbtbVqse0prFdJzNbdtPo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=04MZy/pehBozjAZpO3cljB3DV0/OoPpyks87KLw+g5gV2Zfva8c3ZDYg5C4S8SxDA 3x827RqotUbNiDxdMEBUIYjFZh5XKD87f9avoi9pYAUXJuM4654xC7sylSZE8osjDw aP6ZLzk77RjeCnz6d1nevh4smi4wbkXra8zxCbBA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730981AbfHZN3Z (ORCPT ); Mon, 26 Aug 2019 09:29:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:60658 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727095AbfHZN3Y (ORCPT ); Mon, 26 Aug 2019 09:29:24 -0400 Received: from localhost (unknown [89.205.128.246]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5E6752053B; Mon, 26 Aug 2019 13:29:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566826163; bh=B8w4oTKAlSq8ZbOEvl/7t4CbtbVqse0prFdJzNbdtPo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LaaTm62jYNx2f2wor1dbjtx3gGJgN01k6hNOvw5pBnU2nkirrp7fK+Xvi4BGeIFur UOv5YPD0CsjgPZiQe4UBTcrPZLALyMeDCxvLe1Z2BWhPJteMiXrKTnGL+jGrUivXkf 861K/LXfpYAEvubpifQa+r8rai0lUTXgkVzBuLtk= Date: Mon, 26 Aug 2019 15:29:16 +0200 From: Greg Kroah-Hartman To: Tetsuo Handa Cc: Arnd Bergmann , linux-kernel@vger.kernel.org, Linus Torvalds , syzbot Subject: Re: [PATCH v3] /dev/mem: Bail out upon SIGKILL. Message-ID: <20190826132916.GB12281@kroah.com> References: <1566825205-10703-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1566825205-10703-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 26, 2019 at 10:13:25PM +0900, Tetsuo Handa wrote: > syzbot found that a thread can stall for minutes inside read_mem() or > write_mem() after that thread was killed by SIGKILL [1]. Reading from > iomem areas of /dev/mem can be slow, depending on the hardware. > While reading 2GB at one read() is legal, delaying termination of killed > thread for minutes is bad. Thus, allow reading/writing /dev/mem and > /dev/kmem to be preemptible and killable. > > [ 1335.912419][T20577] read_mem: sz=4096 count=2134565632 > [ 1335.943194][T20577] read_mem: sz=4096 count=2134561536 > [ 1335.978280][T20577] read_mem: sz=4096 count=2134557440 > [ 1336.011147][T20577] read_mem: sz=4096 count=2134553344 > [ 1336.041897][T20577] read_mem: sz=4096 count=2134549248 > > Theoretically, reading/writing /dev/mem and /dev/kmem can become > "interruptible". But this patch chose "killable". Future patch will make > them "interruptible" so that we can revert to "killable" if some program > regressed. > > [1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e > > Signed-off-by: Tetsuo Handa > Reported-by: syzbot > --- > drivers/char/mem.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) What changed from previous versions? That goes below the --- line at the very least. thanks, greg k-h