From 3be7f32878e742cf3c17b435c90e198862457706 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Mon, 12 Oct 2015 10:53:39 -0400 Subject: [PATCH] svcrdma: Fix NFS server crash triggered by 1MB NFS WRITE 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 Signed-off-by: J. Bruce Fields --- net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index 5f6ca47092b0..f0c3ff67ca98 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -533,7 +533,7 @@ 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. */ -- 2.39.5