> -----Original Message----- > From: linux-nfs-owner@xxxxxxxxxxxxxxx [mailto:linux-nfs-owner@xxxxxxxxxxxxxxx] On Behalf Of Chuck Lever > Sent: Sunday, October 04, 2015 10:03 PM > To: linux-nfs@xxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx > 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 <chuck.lever@xxxxxxxxxx> > --- > > This fixes a 4.3-rc regression. Please apply to 4.3-rc when this > patch passes review. > > It could also be appropriate for stable kernels which do not have > commit 7e5be28827bf ("svcrdma: advertise the correct max payload"), > though I have not tested them with this patch. > > 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. */ > Reviewed-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
