Merge tag 'nfsd-4.13-2' of git://linux-nfs.org/~bfields/linux

Pull nfsd fixes from Bruce Fields:
 "Two nfsd bugfixes, neither 4.13 regressions, but both potentially
  serious"

* tag 'nfsd-4.13-2' of git://linux-nfs.org/~bfields/linux:
  net: sunrpc: svcsock: fix NULL-pointer exception
  nfsd: Limit end of page list when decoding NFSv4 WRITE

fs/nfsd/nfs4xdr.c

@@ -144,7 +144,7 @@ static void next_decode_page(struct nfsd4_compoundargs *argp)
 	argp->p = page_address(argp->pagelist[0]);
 	argp->pagelist++;
 	if (argp->pagelen < PAGE_SIZE) {
-		argp->end = argp->p + (argp->pagelen>>2);
+		argp->end = argp->p + XDR_QUADLEN(argp->pagelen);
 		argp->pagelen = 0;
 	} else {
 		argp->end = argp->p + (PAGE_SIZE>>2);
@@ -1279,9 +1279,7 @@ nfsd4_decode_write(struct nfsd4_compoundargs *argp, struct nfsd4_write *write)
 		argp->pagelen -= pages * PAGE_SIZE;
 		len -= pages * PAGE_SIZE;
 
-		argp->p = (__be32 *)page_address(argp->pagelist[0]);
-		argp->pagelist++;
-		argp->end = argp->p + XDR_QUADLEN(PAGE_SIZE);
+		next_decode_page(argp);
 	}
 	argp->p += XDR_QUADLEN(len);
 

net/sunrpc/svcsock.c

@@ -421,6 +421,9 @@ static void svc_data_ready(struct sock *sk)
 		dprintk("svc: socket %p(inet %p), busy=%d\n",
 			svsk, sk,
 			test_bit(XPT_BUSY, &svsk->sk_xprt.xpt_flags));
+
+		/* Refer to svc_setup_socket() for details. */
+		rmb();
 		svsk->sk_odata(sk);
 		if (!test_and_set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags))
 			svc_xprt_enqueue(&svsk->sk_xprt);
@@ -437,6 +440,9 @@ static void svc_write_space(struct sock *sk)
 	if (svsk) {
 		dprintk("svc: socket %p(inet %p), write_space busy=%d\n",
 			svsk, sk, test_bit(XPT_BUSY, &svsk->sk_xprt.xpt_flags));
+
+		/* Refer to svc_setup_socket() for details. */
+		rmb();
 		svsk->sk_owspace(sk);
 		svc_xprt_enqueue(&svsk->sk_xprt);
 	}
@@ -760,8 +766,12 @@ static void svc_tcp_listen_data_ready(struct sock *sk)
 	dprintk("svc: socket %p TCP (listen) state change %d\n",
 		sk, sk->sk_state);
 
-	if (svsk)
+	if (svsk) {
+		/* Refer to svc_setup_socket() for details. */
+		rmb();
 		svsk->sk_odata(sk);
+	}
+
 	/*
 	 * This callback may called twice when a new connection
 	 * is established as a child socket inherits everything
@@ -794,6 +804,8 @@ static void svc_tcp_state_change(struct sock *sk)
 	if (!svsk)
 		printk("svc: socket %p: no user data\n", sk);
 	else {
+		/* Refer to svc_setup_socket() for details. */
+		rmb();
 		svsk->sk_ostate(sk);
 		if (sk->sk_state != TCP_ESTABLISHED) {
 			set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
@@ -1381,12 +1393,18 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
 		return ERR_PTR(err);
 	}
 
-	inet->sk_user_data = svsk;
 	svsk->sk_sock = sock;
 	svsk->sk_sk = inet;
 	svsk->sk_ostate = inet->sk_state_change;
 	svsk->sk_odata = inet->sk_data_ready;
 	svsk->sk_owspace = inet->sk_write_space;
+	/*
+	 * This barrier is necessary in order to prevent race condition
+	 * with svc_data_ready(), svc_listen_data_ready() and others
+	 * when calling callbacks above.
+	 */
+	wmb();
+	inet->sk_user_data = svsk;
 
 	/* Initialize the socket */
 	if (sock->type == SOCK_DGRAM)