From a6b31d18b02ff9d7915c5898c9b5ca41a798cd73 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Fri, 8 Nov 2013 16:03:50 -0500 Subject: SUNRPC: Fix a data corruption issue when retransmitting RPC calls The following scenario can cause silent data corruption when doing NFS writes. It has mainly been observed when doing database writes using O_DIRECT. 1) The RPC client uses sendpage() to do zero-copy of the page data. 2) Due to networking issues, the reply from the server is delayed, and so the RPC client times out. 3) The client issues a second sendpage of the page data as part of an RPC call retransmission. 4) The reply to the first transmission arrives from the server _before_ the client hardware has emptied the TCP socket send buffer. 5) After processing the reply, the RPC state machine rules that the call to be done, and triggers the completion callbacks. 6) The application notices the RPC call is done, and reuses the pages to store something else (e.g. a new write). 7) The client NIC drains the TCP socket send buffer. Since the page data has now changed, it reads a corrupted version of the initial RPC call, and puts it on the wire. This patch fixes the problem in the following manner: The ordering guarantees of TCP ensure that when the server sends a reply, then we know that the _first_ transmission has completed. Using zero-copy in that situation is therefore safe. If a time out occurs, we then send the retransmission using sendmsg() (i.e. no zero-copy), We then know that the socket contains a full copy of the data, and so it will retransmit a faithful reproduction even if the RPC call completes, and the application reuses the O_DIRECT buffer in the meantime. Signed-off-by: Trond Myklebust Cc: stable@vger.kernel.org --- net/sunrpc/xprtsock.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) (limited to 'net') diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 17c88928b7db..dd9d295813cf 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -393,8 +393,10 @@ static int xs_send_kvec(struct socket *sock, struct sockaddr *addr, int addrlen, return kernel_sendmsg(sock, &msg, NULL, 0, 0); } -static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned int base, int more) +static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned int base, int more, bool zerocopy) { + ssize_t (*do_sendpage)(struct socket *sock, struct page *page, + int offset, size_t size, int flags); struct page **ppage; unsigned int remainder; int err, sent = 0; @@ -403,6 +405,9 @@ static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned i base += xdr->page_base; ppage = xdr->pages + (base >> PAGE_SHIFT); base &= ~PAGE_MASK; + do_sendpage = sock->ops->sendpage; + if (!zerocopy) + do_sendpage = sock_no_sendpage; for(;;) { unsigned int len = min_t(unsigned int, PAGE_SIZE - base, remainder); int flags = XS_SENDMSG_FLAGS; @@ -410,7 +415,7 @@ static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned i remainder -= len; if (remainder != 0 || more) flags |= MSG_MORE; - err = sock->ops->sendpage(sock, *ppage, base, len, flags); + err = do_sendpage(sock, *ppage, base, len, flags); if (remainder == 0 || err != len) break; sent += err; @@ -431,9 +436,10 @@ static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned i * @addrlen: UDP only -- length of destination address * @xdr: buffer containing this request * @base: starting position in the buffer + * @zerocopy: true if it is safe to use sendpage() * */ -static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base) +static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, bool zerocopy) { unsigned int remainder = xdr->len - base; int err, sent = 0; @@ -461,7 +467,7 @@ static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, if (base < xdr->page_len) { unsigned int len = xdr->page_len - base; remainder -= len; - err = xs_send_pagedata(sock, xdr, base, remainder != 0); + err = xs_send_pagedata(sock, xdr, base, remainder != 0, zerocopy); if (remainder == 0 || err != len) goto out; sent += err; @@ -564,7 +570,7 @@ static int xs_local_send_request(struct rpc_task *task) req->rq_svec->iov_base, req->rq_svec->iov_len); status = xs_sendpages(transport->sock, NULL, 0, - xdr, req->rq_bytes_sent); + xdr, req->rq_bytes_sent, true); dprintk("RPC: %s(%u) = %d\n", __func__, xdr->len - req->rq_bytes_sent, status); if (likely(status >= 0)) { @@ -620,7 +626,7 @@ static int xs_udp_send_request(struct rpc_task *task) status = xs_sendpages(transport->sock, xs_addr(xprt), xprt->addrlen, xdr, - req->rq_bytes_sent); + req->rq_bytes_sent, true); dprintk("RPC: xs_udp_send_request(%u) = %d\n", xdr->len - req->rq_bytes_sent, status); @@ -693,6 +699,7 @@ static int xs_tcp_send_request(struct rpc_task *task) struct rpc_xprt *xprt = req->rq_xprt; struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt); struct xdr_buf *xdr = &req->rq_snd_buf; + bool zerocopy = true; int status; xs_encode_stream_record_marker(&req->rq_snd_buf); @@ -700,13 +707,20 @@ static int xs_tcp_send_request(struct rpc_task *task) xs_pktdump("packet data:", req->rq_svec->iov_base, req->rq_svec->iov_len); + /* Don't use zero copy if this is a resend. If the RPC call + * completes while the socket holds a reference to the pages, + * then we may end up resending corrupted data. + */ + if (task->tk_flags & RPC_TASK_SENT) + zerocopy = false; /* Continue transmitting the packet/record. We must be careful * to cope with writespace callbacks arriving _after_ we have * called sendmsg(). */ while (1) { status = xs_sendpages(transport->sock, - NULL, 0, xdr, req->rq_bytes_sent); + NULL, 0, xdr, req->rq_bytes_sent, + zerocopy); dprintk("RPC: xs_tcp_send_request(%u) = %d\n", xdr->len - req->rq_bytes_sent, status); -- cgit v1.2.3 From d07ba8422f1e58be94cc98a1f475946dc1b89f1b Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Tue, 12 Nov 2013 17:24:36 -0500 Subject: SUNRPC: Avoid deep recursion in rpc_release_client In cases where an rpc client has a parent hierarchy, then rpc_free_client may end up calling rpc_release_client() on the parent, thus recursing back into rpc_free_client. If the hierarchy is deep enough, then we can get into situations where the stack simply overflows. The fix is to have rpc_release_client() loop so that it can take care of the parent rpc client hierarchy without needing to recurse. Reported-by: Jeff Layton Reported-by: Weston Andros Adamson Reported-by: Bruce Fields Link: http://lkml.kernel.org/r/2C73011F-0939-434C-9E4D-13A1EB1403D7@netapp.com Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust --- net/sunrpc/clnt.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) (limited to 'net') diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index dab09dac8fc7..f09b7db2c492 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -750,14 +750,16 @@ EXPORT_SYMBOL_GPL(rpc_shutdown_client); /* * Free an RPC client */ -static void +static struct rpc_clnt * rpc_free_client(struct rpc_clnt *clnt) { + struct rpc_clnt *parent = NULL; + dprintk_rcu("RPC: destroying %s client for %s\n", clnt->cl_program->name, rcu_dereference(clnt->cl_xprt)->servername); if (clnt->cl_parent != clnt) - rpc_release_client(clnt->cl_parent); + parent = clnt->cl_parent; rpc_clnt_remove_pipedir(clnt); rpc_unregister_client(clnt); rpc_free_iostats(clnt->cl_metrics); @@ -766,18 +768,17 @@ rpc_free_client(struct rpc_clnt *clnt) rpciod_down(); rpc_free_clid(clnt); kfree(clnt); + return parent; } /* * Free an RPC client */ -static void +static struct rpc_clnt * rpc_free_auth(struct rpc_clnt *clnt) { - if (clnt->cl_auth == NULL) { - rpc_free_client(clnt); - return; - } + if (clnt->cl_auth == NULL) + return rpc_free_client(clnt); /* * Note: RPCSEC_GSS may need to send NULL RPC calls in order to @@ -788,7 +789,8 @@ rpc_free_auth(struct rpc_clnt *clnt) rpcauth_release(clnt->cl_auth); clnt->cl_auth = NULL; if (atomic_dec_and_test(&clnt->cl_count)) - rpc_free_client(clnt); + return rpc_free_client(clnt); + return NULL; } /* @@ -799,10 +801,13 @@ rpc_release_client(struct rpc_clnt *clnt) { dprintk("RPC: rpc_release_client(%p)\n", clnt); - if (list_empty(&clnt->cl_tasks)) - wake_up(&destroy_wait); - if (atomic_dec_and_test(&clnt->cl_count)) - rpc_free_auth(clnt); + do { + if (list_empty(&clnt->cl_tasks)) + wake_up(&destroy_wait); + if (!atomic_dec_and_test(&clnt->cl_count)) + break; + clnt = rpc_free_auth(clnt); + } while (clnt != NULL); } EXPORT_SYMBOL_GPL(rpc_release_client); -- cgit v1.2.3