From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932564AbXAWAXE (ORCPT ); Mon, 22 Jan 2007 19:23:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932548AbXAWAWy (ORCPT ); Mon, 22 Jan 2007 19:22:54 -0500 Received: from cantor.suse.de ([195.135.220.2]:35117 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932528AbXAWAWp (ORCPT ); Mon, 22 Jan 2007 19:22:45 -0500 From: NeilBrown To: Andrew Morton Date: Tue, 23 Jan 2007 11:22:18 +1100 Message-Id: <1070123002218.27842@suse.de> X-face: [Gw_3E*Gng}4rRrKRYotwlE?.2|**#s9D Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org NFSd assumes that largest number of pages that will be needed for a request+response is 2+N where N pages is the size of the largest permitted read/write request. The '2' are 1 for the non-data part of the request, and 1 for the non-data part of the reply. However, when a read request is not page-aligned, and we choose to use ->sendfile to send it directly from the page cache, we may need N+1 pages to hold the whole reply. This can overflow and array and cause an Oops. This patch increases size of the array for holding pages by one and makes sure that entry is NULL when it is not in use. Signed-off-by: Neil Brown ### Diffstat output ./fs/nfsd/vfs.c | 3 ++- ./include/linux/sunrpc/svc.h | 5 ++++- ./net/sunrpc/svcsock.c | 2 ++ 3 files changed, 8 insertions(+), 2 deletions(-) diff .prev/fs/nfsd/vfs.c ./fs/nfsd/vfs.c --- .prev/fs/nfsd/vfs.c 2007-01-23 11:13:45.000000000 +1100 +++ ./fs/nfsd/vfs.c 2007-01-23 11:14:54.000000000 +1100 @@ -822,7 +822,8 @@ nfsd_read_actor(read_descriptor_t *desc, rqstp->rq_res.page_len = size; } else if (page != pp[-1]) { get_page(page); - put_page(*pp); + if (*pp) + put_page(*pp); *pp = page; rqstp->rq_resused++; rqstp->rq_res.page_len += size; diff .prev/include/linux/sunrpc/svc.h ./include/linux/sunrpc/svc.h --- .prev/include/linux/sunrpc/svc.h 2007-01-23 11:13:45.000000000 +1100 +++ ./include/linux/sunrpc/svc.h 2007-01-23 11:14:54.000000000 +1100 @@ -144,8 +144,11 @@ extern u32 svc_max_payload(const struct * * Each request/reply pair can have at most one "payload", plus two pages, * one for the request, and one for the reply. + * We using ->sendfile to return read data, we might need one extra page + * if the request is not page-aligned. So add another '1'. */ -#define RPCSVC_MAXPAGES ((RPCSVC_MAXPAYLOAD+PAGE_SIZE-1)/PAGE_SIZE + 2) +#define RPCSVC_MAXPAGES ((RPCSVC_MAXPAYLOAD+PAGE_SIZE-1)/PAGE_SIZE \ + + 2 + 1) static inline u32 svc_getnl(struct kvec *iov) { diff .prev/net/sunrpc/svcsock.c ./net/sunrpc/svcsock.c --- .prev/net/sunrpc/svcsock.c 2007-01-23 11:13:45.000000000 +1100 +++ ./net/sunrpc/svcsock.c 2007-01-23 11:14:54.000000000 +1100 @@ -1306,6 +1306,8 @@ svc_recv(struct svc_rqst *rqstp, long ti schedule_timeout_uninterruptible(msecs_to_jiffies(500)); rqstp->rq_pages[i] = p; } + rqstp->rq_pages[i++] = NULL; /* this might be seen in nfs_read_actor */ + BUG_ON(pages >= RPCSVC_MAXPAGES); /* Make arg->head point to first page and arg->pages point to rest */ arg = &rqstp->rq_arg;