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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 0FEEAC433E1 for ; Thu, 13 Aug 2020 15:37:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD1E020781 for ; Thu, 13 Aug 2020 15:37:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726427AbgHMPh0 (ORCPT ); Thu, 13 Aug 2020 11:37:26 -0400 Received: from verein.lst.de ([213.95.11.211]:46752 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726249AbgHMPhZ (ORCPT ); Thu, 13 Aug 2020 11:37:25 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id C439A68AFE; Thu, 13 Aug 2020 17:37:22 +0200 (CEST) Date: Thu, 13 Aug 2020 17:37:22 +0200 From: Christoph Hellwig To: Josef Bacik Cc: hch@lst.de, viro@ZenIV.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-team@fb.com, willy@infradead.org Subject: Re: [PATCH][v2] proc: use vmalloc for our kernel buffer Message-ID: <20200813153722.GA13844@lst.de> References: <20200813145305.805730-1-josef@toxicpanda.com> <20200813153356.857625-1-josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200813153356.857625-1-josef@toxicpanda.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Aug 13, 2020 at 11:33:56AM -0400, Josef Bacik wrote: > Since > > sysctl: pass kernel pointers to ->proc_handler > > we have been pre-allocating a buffer to copy the data from the proc > handlers into, and then copying that to userspace. The problem is this > just blind kmalloc()'s the buffer size passed in from the read, which in > the case of our 'cat' binary was 64kib. Order-4 allocations are not > awesome, and since we can potentially allocate up to our maximum order, > use vmalloc for these buffers. > > Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler") > Signed-off-by: Josef Bacik > --- > v1->v2: > - Make vmemdup_user_nul actually do the right thing...sorry about that. > > fs/proc/proc_sysctl.c | 6 +++--- > include/linux/string.h | 1 + > mm/util.c | 27 +++++++++++++++++++++++++++ > 3 files changed, 31 insertions(+), 3 deletions(-) > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > index 6c1166ccdaea..207ac6e6e028 100644 > --- a/fs/proc/proc_sysctl.c > +++ b/fs/proc/proc_sysctl.c > @@ -571,13 +571,13 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf, > goto out; > > if (write) { > - kbuf = memdup_user_nul(ubuf, count); > + kbuf = vmemdup_user_nul(ubuf, count); Given that this can also do a kmalloc and thus needs to be paired with kvfree shouldn't it be kvmemdup_user_nul?