Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frank Sorenson , "J. Bruce Fields" Subject: [PATCH 4.9 69/83] sunrpc: correct the computation for page_ptr when truncating Date: Mon, 19 Nov 2018 17:29:35 +0100 Message-Id: <20181119162625.639258964@linuxfoundation.org> In-Reply-To: <20181119162612.046511542@linuxfoundation.org> References: <20181119162612.046511542@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frank Sorenson commit 5d7a5bcb67c70cbc904057ef52d3fcfeb24420bb upstream. When truncating the encode buffer, the page_ptr is getting advanced, causing the next page to be skipped while encoding. The page is still included in the response, so the response contains a page of bogus data. We need to adjust the page_ptr backwards to ensure we encode the next page into the correct place. We saw this triggered when concurrent directory modifications caused nfsd4_encode_direct_fattr() to return nfserr_noent, and the resulting call to xdr_truncate_encode() corrupted the READDIR reply. Signed-off-by: Frank Sorenson Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xdr.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -639,11 +639,10 @@ void xdr_truncate_encode(struct xdr_stre WARN_ON_ONCE(xdr->iov); return; } - if (fraglen) { + if (fraglen) xdr->end = head->iov_base + head->iov_len; - xdr->page_ptr--; - } /* (otherwise assume xdr->end is already set) */ + xdr->page_ptr--; head->iov_len = len; buf->len = len; xdr->p = head->iov_base + head->iov_len;