From patchwork Thu Mar 9 18:56:27 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 9614027 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A440060417 for ; Thu, 9 Mar 2017 19:02:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9EF3026E3A for ; Thu, 9 Mar 2017 19:02:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 903B22849A; Thu, 9 Mar 2017 19:02:27 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2B651223A6 for ; Thu, 9 Mar 2017 19:02:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932964AbdCIS4e (ORCPT ); Thu, 9 Mar 2017 13:56:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40136 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932956AbdCIS4a (ORCPT ); Thu, 9 Mar 2017 13:56:30 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C3457C01B7E6; Thu, 9 Mar 2017 18:56:30 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-66.rdu2.redhat.com [10.10.120.66] (may be forged)) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v29IuTPw013102; Thu, 9 Mar 2017 13:56:29 -0500 Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 06/27] afs: Handle better the server returning excess or short data From: David Howells To: viro@ZenIV.linux.org.uk Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Date: Thu, 09 Mar 2017 18:56:27 +0000 Message-ID: <148908578785.16794.7409042023189133705.stgit@warthog.procyon.org.uk> In-Reply-To: <148908574888.16794.14109877851518811944.stgit@warthog.procyon.org.uk> References: <148908574888.16794.14109877851518811944.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 09 Mar 2017 18:56:30 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When an AFS server is given an FS.FetchData{,64} request to read data from a file, it is permitted by the protocol to return more or less than was requested. kafs currently relies on the latter behaviour in readpage{,s} to handle a partial page at the end of the file (we just ask for a whole page and clear space beyond the short read). However, we don't handle all cases. Add: (1) Handle excess data by discarding it rather than aborting. Note that we use a common static buffer to discard into so that the decryption algorithm advances the PCBC state. (2) Handle a short read that affects more than just the last page. Note that if a read comes up unexpectedly short of long, it's possible that the server's copy of the file changed - in which case the data version number will have been incremented and the callback will have been broken - in which case all the pages currently attached to the inode will be zapped anyway at some point. Signed-off-by: David Howells --- fs/afs/file.c | 7 +++++-- fs/afs/fsclient.c | 49 +++++++++++++++++++++++++++++++++++-------------- 2 files changed, 40 insertions(+), 16 deletions(-) diff --git a/fs/afs/file.c b/fs/afs/file.c index ba7b71fba34b..a38e1c30d110 100644 --- a/fs/afs/file.c +++ b/fs/afs/file.c @@ -184,10 +184,13 @@ int afs_page_filler(void *data, struct page *page) if (!req) goto enomem; + /* We request a full page. If the page is a partial one at the + * end of the file, the server will return a short read and the + * unmarshalling code will clear the unfilled space. + */ atomic_set(&req->usage, 1); req->pos = (loff_t)page->index << PAGE_SHIFT; - req->len = min_t(size_t, i_size_read(inode) - req->pos, - PAGE_SIZE); + req->len = PAGE_SIZE; req->nr_pages = 1; req->pages[0] = page; get_page(page); diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c index ac8e766978dc..bf8904a1a58f 100644 --- a/fs/afs/fsclient.c +++ b/fs/afs/fsclient.c @@ -17,6 +17,12 @@ #include "afs_fs.h" /* + * We need somewhere to discard into in case the server helpfully returns more + * than we asked for in FS.FetchData{,64}. + */ +static u8 afs_discard_buffer[64]; + +/* * decode an AFSFid block */ static void xdr_decode_AFSFid(const __be32 **_bp, struct afs_fid *fid) @@ -353,12 +359,6 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call) req->actual_len |= ntohl(call->tmp); _debug("DATA length: %llu", req->actual_len); - /* Check that the server didn't want to send us extra. We - * might want to just discard instead, but that requires - * cooperation from AF_RXRPC. - */ - if (req->actual_len > req->len) - return -EBADMSG; req->remain = req->actual_len; call->offset = req->pos & (PAGE_SIZE - 1); @@ -368,6 +368,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call) call->unmarshall++; begin_page: + ASSERTCMP(req->index, <, req->nr_pages); if (req->remain > PAGE_SIZE - call->offset) size = PAGE_SIZE - call->offset; else @@ -390,18 +391,37 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call) if (req->page_done) req->page_done(call, req); if (req->remain > 0) { - req->index++; call->offset = 0; + req->index++; + if (req->index >= req->nr_pages) + goto begin_discard; goto begin_page; } } + goto no_more_data; + + /* Discard any excess data the server gave us */ + begin_discard: + case 4: + size = min_t(size_t, sizeof(afs_discard_buffer), req->remain); + call->count = size; + _debug("extract discard %u/%llu %zu/%u", + req->remain, req->actual_len, call->offset, call->count); + + call->offset = 0; + ret = afs_extract_data(call, afs_discard_buffer, call->count, true); + req->remain -= call->offset; + if (ret < 0) + return ret; + if (req->remain > 0) + goto begin_discard; no_more_data: call->offset = 0; - call->unmarshall++; + call->unmarshall = 5; /* extract the metadata */ - case 4: + case 5: ret = afs_extract_data(call, call->buffer, (21 + 3 + 6) * 4, false); if (ret < 0) @@ -416,16 +436,17 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call) call->offset = 0; call->unmarshall++; - case 5: + case 6: break; } - if (call->count < PAGE_SIZE) { - buffer = kmap(req->pages[req->index]); - memset(buffer + call->count, 0, PAGE_SIZE - call->count); - kunmap(req->pages[req->index]); + for (; req->index < req->nr_pages; req->index++) { + if (call->count < PAGE_SIZE) + zero_user_segment(req->pages[req->index], + call->count, PAGE_SIZE); if (req->page_done) req->page_done(call, req); + call->count = 0; } _leave(" = 0 [done]");