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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C56D1C74A5B for ; Fri, 17 Mar 2023 13:06:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229717AbjCQNG2 (ORCPT ); Fri, 17 Mar 2023 09:06:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229590AbjCQNG1 (ORCPT ); Fri, 17 Mar 2023 09:06:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC298E20C7 for ; Fri, 17 Mar 2023 06:06:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3CC20622A8 for ; Fri, 17 Mar 2023 13:06:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F681C433EF; Fri, 17 Mar 2023 13:06:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679058385; bh=2NhrvGoNWJ/ADAH7N47NMv95p5ATV6Qx6LQ/dmllofw=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Q5eiqFM+FISX97jSAi1tLgg9pxUUE+SYv0E1g/mvVEm7AUXdrhB1OewKR88Z6zmnn WOdGggEQ8R0QaEKCiqakpMGc1G7TdjNLJnuJ0FLUH2exPlHgc7eOu1XSeV8UckecAm blTR6QUyL5QOfbdMkWCwxNnEiYHHX9cVWrbI20K6lvgIEGtCJuTOiq8lvgMki5uTU4 zt5Bqk3WIs75kJnomRqE4KEHzNucW9/ffyQzW1xi9S5v3qe+le7UaDk8DEfS1sBwu3 qtWVDAUyj/ooqDp6BoSlM0gco6sNN/Qq3KW4yEtsuXbq3xDd6xpI9Vw0aoZPbbQfhf oIvvYzcOnjnwA== Message-ID: Subject: Re: [PATCH 1/2] nfsd: don't replace page in rq_pages if it's a continuation of last page From: Jeff Layton To: chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, dcritch@redhat.com, d.lesca@solinos.it Date: Fri, 17 Mar 2023 09:06:23 -0400 In-Reply-To: <20230317105608.19393-1-jlayton@kernel.org> References: <20230317105608.19393-1-jlayton@kernel.org> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, 2023-03-17 at 06:56 -0400, Jeff Layton wrote: > The splice read calls nfsd_splice_actor to put the pages containing file > data into the svc_rqst->rq_pages array. It's possible however to get a > splice result that only has a partial page at the end, if (e.g.) the > filesystem hands back a short read that doesn't cover the whole page. >=20 > nfsd_splice_actor will plop the partial page into its rq_pages array and > return. Then later, when nfsd_splice_actor is called again, the > remainder of the page may end up being filled out. At this point, > nfsd_splice_actor will put the page into the array _again_ corrupting > the reply. If this is done enough times, rq_next_page will overrun the > array and corrupt the trailing fields -- the rq_respages and > rq_next_page pointers themselves. >=20 > If we've already added the page to the array in the last pass, don't add > it to the array a second time when dealing with a splice continuation. > This was originally handled properly in nfsd_splice_actor, but commit > 91e23b1c3982 removed the check for it, and started universally replacing > pages. >=20 > Fixes: 91e23b1c3982 ("NFSD: Clean up nfsd_splice_actor()") > Reported-by: Dario Lesca > Tested-by: David Critch > Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D2150630 > Signed-off-by: Jeff Layton > --- > fs/nfsd/vfs.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 502e1b7742db..3709ef57d96e 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -941,8 +941,11 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, stru= ct pipe_buffer *buf, > struct page *last_page; > =20 > last_page =3D page + (offset + sd->len - 1) / PAGE_SIZE; > - for (page +=3D offset / PAGE_SIZE; page <=3D last_page; page++) > - svc_rqst_replace_page(rqstp, page); > + for (page +=3D offset / PAGE_SIZE; page <=3D last_page; page++) { > + /* Only replace page if we haven't already done so */ Note that I think that this was probably the real rationale for the pp[- 1] check that 91e23b1c3982 removed. Given that, maybe we should flesh this comment out a bit more for posterity? /* * When we're splicing from a pipe, it's possible that * we'll get an incomplete page that may be updated on * a later call. Only splice it into rq_pages once. */ > + if (page !=3D *(rqstp->rq_next_page - 1)) > + svc_rqst_replace_page(rqstp, page); > + } > if (rqstp->rq_res.page_len =3D=3D 0) // first call > rqstp->rq_res.page_base =3D offset % PAGE_SIZE; > rqstp->rq_res.page_len +=3D sd->len; --=20 Jeff Layton