From patchwork Mon Mar 4 03:08:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10837305 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 08AD31575 for ; Mon, 4 Mar 2019 03:08:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D724D2883F for ; Mon, 4 Mar 2019 03:08:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C6A0929C2C; Mon, 4 Mar 2019 03:08:33 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham 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 4DEB32883F for ; Mon, 4 Mar 2019 03:08:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725974AbfCDDIb (ORCPT ); Sun, 3 Mar 2019 22:08:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:41782 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725938AbfCDDIb (ORCPT ); Sun, 3 Mar 2019 22:08:31 -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 622F1AEDF; Mon, 4 Mar 2019 03:08:30 +0000 (UTC) From: NeilBrown To: "J. Bruce Fields" , Jeff Layton Date: Mon, 04 Mar 2019 14:08:22 +1100 Subject: [PATCH] nfsd: fix memory corruption caused by readdir cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <87lg1vs5eh.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the result of an NFSv3 readdir{,plus} request results in the "offset" on one entry having to be split across 2 pages, and is sized so that the next directory entry doesn't fix in the requested size, then memory corruption can happen. When encode_entry() is called after encoding the last entry that fits, it notices that ->offset and ->offset1 are set, and so stores the offset value in the two pages as required. It clears ->offset1 but *does not* clear ->offset. Normally this omission doesn't matter as encode_entry_baggage() will be called, and will set ->offset to a suitable value (not on a page boundary). But in the case where cd->buflen < elen and nfserr_toosmall is returned, ->offset is not reset. This means that nfsd3proc_readdirplus will see ->offset with a value 4 bytes before the end of a page, and ->offset1 set to NULL. It will try to write 8bytes to ->offset. If we are lucky, the next page will be read-only, and the system will BUG: unable to handle kernel paging request at... If we are unlucky, some innocent page will have the first 4 bytes corrupted. nfsd3proc_readdir() doesn't even check for ->offset1, it just blindly writes 8 bytes to the offset wherever it is. Fix this by clearing ->offset after it is used, and copying the ->offset handling code from nfsd3_proc_readdirplus into nfsd3_proc_readdir. (Note that the commit hash in the Fixes tag is from the 'history' tree - this bug predates git). Fixes: eb229d253e6c ("[PATCH] kNFSd: fix two xdr-encode bugs for readdirplus reply") Cc: stable@vger.kernel.org (v2.6.12+) Signed-off-by: NeilBrown --- Can I still get extra credit for fixing a bug that is 14.5 years old, if I'm the one who introduced it? fs/nfsd/nfs3proc.c | 16 ++++++++++++++-- fs/nfsd/nfs3xdr.c | 1 + 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index 9eb8086ea841..c9cf46e0c040 100644 --- a/fs/nfsd/nfs3proc.c +++ b/fs/nfsd/nfs3proc.c @@ -463,8 +463,19 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp) &resp->common, nfs3svc_encode_entry); memcpy(resp->verf, argp->verf, 8); resp->count = resp->buffer - argp->buffer; - if (resp->offset) - xdr_encode_hyper(resp->offset, argp->cookie); + if (resp->offset) { + loff_t offset = argp->cookie; + + if (unlikely(resp->offset1)) { + /* we ended up with offset on a page boundary */ + *resp->offset = htonl(offset >> 32); + *resp->offset1 = htonl(offset & 0xffffffff); + resp->offset1 = NULL; + } else { + xdr_encode_hyper(resp->offset, offset); + } + resp->offset = NULL; + } RETURN_STATUS(nfserr); } @@ -533,6 +544,7 @@ nfsd3_proc_readdirplus(struct svc_rqst *rqstp) } else { xdr_encode_hyper(resp->offset, offset); } + resp->offset = NULL; } RETURN_STATUS(nfserr); diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index 9b973f4f7d01..83919116d5cb 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -921,6 +921,7 @@ encode_entry(struct readdir_cd *ccd, const char *name, int namlen, } else { xdr_encode_hyper(cd->offset, offset64); } + cd->offset = NULL; } /*