Fix upcall races in the client side krpc. For the client side upcall,

holding SOCKBUF_LOCK() isn't sufficient to guarantee that there is
no upcall in progress, since SOCKBUF_LOCK() is released/re-acquired
in the upcall. An upcall reference counter was added to the upcall
structure that is incremented at the beginning of the upcall and
decremented at the end of the upcall. As such, a reference count == 0
when holding the SOCKBUF_LOCK() guarantees there is no upcall in
progress. Add a function that is called just after soupcall_clear(),
which waits until the reference count == 0.
Also, move the mtx_destroy() down to after soupcall_clear(), so that
the mutex is not destroyed before upcalls are done.

Reviewed by:	dfr, jhb
Tested by:	pho
Approved by:	kib (mentor)

2 files changed, 53 insertions, 3 deletions

diff --git a/sys/rpc/clnt_dg.c b/sys/rpc/clnt_dg.c
index 880a16f..865c704 100644
--- a/sys/rpc/clnt_dg.c
+++ b/sys/rpc/clnt_dg.c
@@ -123,8 +123,11 @@ struct cu_socket {
 	struct mtx		cs_lock;
 	int			cs_refs;	/* Count of clients */
 	struct cu_request_list	cs_pending;	/* Requests awaiting replies */
+	int			cs_upcallrefs;	/* Refcnt of upcalls in prog.*/
 };
 
+static void clnt_dg_upcallsdone(struct socket *, struct cu_socket *);
+
 /*
  * Private data kept per client handle
  */
@@ -291,6 +294,7 @@ recheck_socket:
 		}
 		mtx_init(&cs->cs_lock, "cs->cs_lock", NULL, MTX_DEF);
 		cs->cs_refs = 1;
+		cs->cs_upcallrefs = 0;
 		TAILQ_INIT(&cs->cs_pending);
 		soupcall_set(so, SO_RCV, clnt_dg_soupcall, cs);
 	}
@@ -988,10 +992,12 @@ clnt_dg_destroy(CLIENT *cl)
 
 	cs->cs_refs--;
 	if (cs->cs_refs == 0) {
-		mtx_destroy(&cs->cs_lock);
+		mtx_unlock(&cs->cs_lock);
 		SOCKBUF_LOCK(&cu->cu_socket->so_rcv);
 		soupcall_clear(cu->cu_socket, SO_RCV);
+		clnt_dg_upcallsdone(cu->cu_socket, cs);
 		SOCKBUF_UNLOCK(&cu->cu_socket->so_rcv);
+		mtx_destroy(&cs->cs_lock);
 		mem_free(cs, sizeof(*cs));
 		lastsocketref = TRUE;
 	} else {
@@ -1036,6 +1042,7 @@ clnt_dg_soupcall(struct socket *so, void *arg, int waitflag)
 	int error, rcvflag, foundreq;
 	uint32_t xid;
 
+	cs->cs_upcallrefs++;
 	uio.uio_resid = 1000000000;
 	uio.uio_td = curthread;
 	do {
@@ -1111,6 +1118,24 @@ clnt_dg_soupcall(struct socket *so, void *arg, int waitflag)
 		if (!foundreq)
 			m_freem(m);
 	} while (m);
+	cs->cs_upcallrefs--;
+	if (cs->cs_upcallrefs < 0)
+		panic("rpcdg upcall refcnt");
+	if (cs->cs_upcallrefs == 0)
+		wakeup(&cs->cs_upcallrefs);
 	return (SU_OK);
 }
 
+/*
+ * Wait for all upcalls in progress to complete.
+ */
+static void
+clnt_dg_upcallsdone(struct socket *so, struct cu_socket *cs)
+{
+
+	SOCKBUF_LOCK_ASSERT(&so->so_rcv);
+
+	while (cs->cs_upcallrefs > 0)
+		(void) msleep(&cs->cs_upcallrefs, SOCKBUF_MTX(&so->so_rcv), 0,
+		    "rpcdgup", 0);
+}
diff --git a/sys/rpc/clnt_vc.c b/sys/rpc/clnt_vc.c
index f094945..4e732f2 100644
--- a/sys/rpc/clnt_vc.c
+++ b/sys/rpc/clnt_vc.c
@@ -137,8 +137,11 @@ struct ct_data {
 	size_t		ct_record_resid; /* how much left of reply to read */
 	bool_t		ct_record_eor;	 /* true if reading last fragment */
 	struct ct_request_list ct_pending;
+	int		ct_upcallrefs;	/* Ref cnt of upcalls in prog. */
 };
 
+static void clnt_vc_upcallsdone(struct ct_data *);
+
 static const char clnt_vc_errstr[] = "%s : %s";
 static const char clnt_vc_str[] = "clnt_vc_create";
 static const char clnt_read_vc_str[] = "read_vc";
@@ -184,6 +187,7 @@ clnt_vc_create(
 	ct->ct_threads = 0;
 	ct->ct_closing = FALSE;
 	ct->ct_closed = FALSE;
+	ct->ct_upcallrefs = 0;
 
 	if ((so->so_state & (SS_ISCONNECTED|SS_ISCONFIRMING)) == 0) {
 		error = soconnect(so, raddr, curthread);
@@ -753,6 +757,7 @@ clnt_vc_close(CLIENT *cl)
 
 		SOCKBUF_LOCK(&ct->ct_socket->so_rcv);
 		soupcall_clear(ct->ct_socket, SO_RCV);
+		clnt_vc_upcallsdone(ct);
 		SOCKBUF_UNLOCK(&ct->ct_socket->so_rcv);
 
 		/*
@@ -825,6 +830,7 @@ clnt_vc_soupcall(struct socket *so, void *arg, int waitflag)
 	uint32_t xid, header;
 	bool_t do_read;
 
+	ct->ct_upcallrefs++;
 	uio.uio_td = curthread;
 	do {
 		/*
@@ -845,7 +851,7 @@ clnt_vc_soupcall(struct socket *so, void *arg, int waitflag)
 				do_read = TRUE;
 
 			if (!do_read)
-				return (SU_OK);
+				break;
 
 			SOCKBUF_UNLOCK(&so->so_rcv);
 			uio.uio_resid = sizeof(uint32_t);
@@ -898,7 +904,7 @@ clnt_vc_soupcall(struct socket *so, void *arg, int waitflag)
 				do_read = TRUE;
 
 			if (!do_read)
-				return (SU_OK);
+				break;
 
 			/*
 			 * We have the record mark. Read as much as
@@ -979,5 +985,24 @@ clnt_vc_soupcall(struct socket *so, void *arg, int waitflag)
 			}
 		}
 	} while (m);
+	ct->ct_upcallrefs--;
+	if (ct->ct_upcallrefs < 0)
+		panic("rpcvc upcall refcnt");
+	if (ct->ct_upcallrefs == 0)
+		wakeup(&ct->ct_upcallrefs);
 	return (SU_OK);
 }
+
+/*
+ * Wait for all upcalls in progress to complete.
+ */
+static void
+clnt_vc_upcallsdone(struct ct_data *ct)
+{
+
+	SOCKBUF_LOCK_ASSERT(&ct->ct_socket->so_rcv);
+
+	while (ct->ct_upcallrefs > 0)
+		(void) msleep(&ct->ct_upcallrefs,
+		    SOCKBUF_MTX(&ct->ct_socket->so_rcv), 0, "rpcvcup", 0);
+}