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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 C0A08C432C3 for ; Fri, 22 Nov 2019 10:47:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9E55320656 for ; Fri, 22 Nov 2019 10:47:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728815AbfKVKr1 (ORCPT ); Fri, 22 Nov 2019 05:47:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:37254 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729131AbfKVKr0 (ORCPT ); Fri, 22 Nov 2019 05:47:26 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 00DA1AE00; Fri, 22 Nov 2019 10:47:24 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 7AC9C1E484C; Fri, 22 Nov 2019 11:47:24 +0100 (CET) Date: Fri, 22 Nov 2019 11:47:24 +0100 From: Jan Kara To: "Darrick J. Wong" Cc: Jan Kara , linux-fsdevel@vger.kernel.org, Christoph Hellwig , Matthew Bobrowski , Eric Biggers , stable@vger.kernel.org Subject: Re: [PATCH 1/2] iomap: Fix pipe page leakage during splicing Message-ID: <20191122104724.GA26721@quack2.suse.cz> References: <20191121161144.30802-1-jack@suse.cz> <20191121161538.18445-1-jack@suse.cz> <20191121235528.GO6211@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191121235528.GO6211@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu 21-11-19 15:55:28, Darrick J. Wong wrote: > On Thu, Nov 21, 2019 at 05:15:34PM +0100, Jan Kara wrote: > > When splicing using iomap_dio_rw() to a pipe, we may leak pipe pages > > because bio_iov_iter_get_pages() records that the pipe will have full > > extent worth of data however if file size is not block size aligned > > iomap_dio_rw() returns less than what bio_iov_iter_get_pages() set up > > and splice code gets confused leaking a pipe page with the file tail. > > > > Handle the situation similarly to the old direct IO implementation and > > revert iter to actually returned read amount which makes iter consistent > > with value returned from iomap_dio_rw() and thus the splice code is > > happy. > > > > Fixes: ff6a9292e6f6 ("iomap: implement direct I/O") > > CC: stable@vger.kernel.org > > Reported-by: syzbot+991400e8eba7e00a26e1@syzkaller.appspotmail.com > > Signed-off-by: Jan Kara > > --- > > fs/iomap/direct-io.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > > index 1fc28c2da279..30189652c560 100644 > > --- a/fs/iomap/direct-io.c > > +++ b/fs/iomap/direct-io.c > > @@ -497,8 +497,15 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > > } > > pos += ret; > > > > - if (iov_iter_rw(iter) == READ && pos >= dio->i_size) > > + if (iov_iter_rw(iter) == READ && pos >= dio->i_size) { > > + /* > > + * We will report we've read data only upto i_size. > > Nit: "up to"; will fix that on the way in. > > > + * Revert iter to a state corresponding to that as > > + * some callers (such as splice code) rely on it. > > + */ > > + iov_iter_revert(iter, pos - dio->i_size); > > Just to make sure I'm getting this right, iov_iter_revert walks the > iterator variables backwards through pipe buffers/bvec/iovec, which has > the effect of undoing whatever iterator walking we've just done. > > In contrast, iov_iter_reexpand undoes a previous subtraction to > iov->count which was (presumably) done via iov_iter_truncate. > > Or to put it another way, _revert walks the iteration pointer backwards, > whereas _truncate/_reexpand modify where the iteration ends. Right? Correct. > Reviewed-by: Darrick J. Wong Thanks! Honza -- Jan Kara SUSE Labs, CR