> On Oct 5, 2015, at 3:42 PM, Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > >> -----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> Thanks! -- 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
