Return-Path: Received: from fieldses.org ([173.255.197.46]:46408 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751116AbbJLRNx (ORCPT ); Mon, 12 Oct 2015 13:13:53 -0400 Date: Mon, 12 Oct 2015 13:13:52 -0400 From: "J. Bruce Fields" To: Chuck Lever Cc: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH] svcrdma: Fix NFS server crash triggered by 1MB NFS WRITE Message-ID: <20151012171352.GC28755@fieldses.org> References: <20151012145257.3981.13852.stgit@oracle-120.nfsv4bat.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20151012145257.3981.13852.stgit@oracle-120.nfsv4bat.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Oct 12, 2015 at 10:53:39AM -0400, Chuck Lever wrote: > Now that the NFS server advertises a maximum payload size of 1MB > for RPC/RDMA again, it crashes in svc_process_common() when NFS > client sends a 1MB NFS WRITE on an NFS/RDMA mount. > > The server has set up a 259 element array of struct page pointers > in rq_pages[] for each incoming request. The last element of the > array is NULL. > > When an incoming request has been completely received, > rdma_read_complete() attempts to set the starting page of the > incoming page vector: > > rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count]; > > and the page to use for the reply: > > rqstp->rq_respages = &rqstp->rq_arg.pages[page_no]; > > But the value of page_no has already accounted for head->hdr_count. > Thus rq_respages now points past the end of the incoming pages. > > For NFS WRITE operations smaller than the maximum, this is harmless. > But when the NFS WRITE operation is as large as the server's max > payload size, rq_respages now points at the last entry in rq_pages, > which is NULL. > > Fixes: cc9a903d915c ('svcrdma: Change maximum server payload . . .') > BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=270 > Signed-off-by: Chuck Lever > Reviewed-by: Sagi Grimberg > Reviewed-by: Steve Wise > Reviewed-by: Shirley Ma > --- > > Hi Bruce- > > This is a regression in 4.3. Can you send this to Linus? OK, queuing for 4.3, thanks.--b. > > > net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > index cb51742..37b4341 100644 > --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > @@ -531,7 +531,7 @@ static int rdma_read_complete(struct svc_rqst *rqstp, > rqstp->rq_arg.page_base = head->arg.page_base; > > /* rq_respages starts after the last arg page */ > - rqstp->rq_respages = &rqstp->rq_arg.pages[page_no]; > + rqstp->rq_respages = &rqstp->rq_pages[page_no]; > rqstp->rq_next_page = rqstp->rq_respages + 1; > > /* Rebuild rq_arg head and tail. */