Make sogetopt(9) caller responsible for allocating an MT_SOOPTS mbuf.

Move a blocking memory allocation out of the socket lock and create
a simpler alloc/free pattern to review.  Now both m_get() and m_free()
are in the same place.

Discussed with bluhm@.

Encouragements from deraadt@ and tedu@, ok kettenis@, florian@, visa@

3 files changed, 10 insertions, 23 deletions

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index c499f46de04..369e32ecdc5 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_socket.c,v 1.201 2017/08/10 19:20:43 mpi Exp $	*/
+/*	$OpenBSD: uipc_socket.c,v 1.202 2017/08/22 09:13:36 mpi Exp $	*/
 /*	$NetBSD: uipc_socket.c,v 1.21 1996/02/04 02:17:52 christos Exp $	*/
 
 /*
@@ -1755,30 +1755,24 @@ bad:
 }
 
 int
-sogetopt(struct socket *so, int level, int optname, struct mbuf **mp)
+sogetopt(struct socket *so, int level, int optname, struct mbuf *m)
 {
 	int error = 0;
-	struct mbuf *m;
 
 	soassertlocked(so);
 
 	if (level != SOL_SOCKET) {
 		if (so->so_proto->pr_ctloutput) {
-			m = m_get(M_WAIT, MT_SOOPTS);
 			m->m_len = 0;
 
 			error = (*so->so_proto->pr_ctloutput)(PRCO_GETOPT, so,
 			    level, optname, m);
-			if (error) {
-				m_free(m);
+			if (error)
 				return (error);
-			}
-			*mp = m;
 			return (0);
 		} else
 			return (ENOPROTOOPT);
 	} else {
-		m = m_get(M_WAIT, MT_SOOPTS);
 		m->m_len = sizeof (int);
 
 		switch (optname) {
@@ -1856,13 +1850,10 @@ sogetopt(struct socket *so, int level, int optname, struct mbuf **mp)
 				level = dom->dom_protosw->pr_protocol;
 				error = (*so->so_proto->pr_ctloutput)
 				    (PRCO_GETOPT, so, level, optname, m);
-				if (error) {
-					(void)m_free(m);
+				if (error)
 					return (error);
-				}
 				break;
 			}
-			(void)m_free(m);
 			return (ENOPROTOOPT);
 
 #ifdef SOCKET_SPLICE
@@ -1887,17 +1878,13 @@ sogetopt(struct socket *so, int level, int optname, struct mbuf **mp)
 					    &(unp->unp_connid), m->m_len);
 					break;
 				}
-				(void)m_free(m);
 				return (ENOTCONN);
 			}
-			(void)m_free(m);
 			return (EOPNOTSUPP);
 
 		default:
-			(void)m_free(m);
 			return (ENOPROTOOPT);
 		}
-		*mp = m;
 		return (0);
 	}
 }
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 047f557274e..bc9b50cfac3 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_syscalls.c,v 1.158 2017/08/10 19:20:43 mpi Exp $	*/
+/*	$OpenBSD: uipc_syscalls.c,v 1.159 2017/08/22 09:13:36 mpi Exp $	*/
 /*	$NetBSD: uipc_syscalls.c,v 1.19 1996/02/09 19:00:48 christos Exp $	*/
 
 /*
@@ -1014,9 +1014,10 @@ sys_getsockopt(struct proc *p, void *v, register_t *retval)
 			goto out;
 	} else
 		valsize = 0;
+	m = m_get(M_WAIT, MT_SOOPTS);
 	so = fp->f_data;
 	s = solock(so);
-	error = sogetopt(so, SCARG(uap, level), SCARG(uap, name), &m);
+	error = sogetopt(so, SCARG(uap, level), SCARG(uap, name), m);
 	sounlock(s);
 	if (error == 0 && SCARG(uap, val) && valsize && m != NULL) {
 		if (valsize > m->m_len)
@@ -1026,9 +1027,9 @@ sys_getsockopt(struct proc *p, void *v, register_t *retval)
 			error = copyout(&valsize,
 			    SCARG(uap, avalsize), sizeof (valsize));
 	}
+	m_free(m);
 out:
 	FRELE(fp, p);
-	m_free(m);
 	return (error);
 }
 
diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
index 83efc2ecbb5..48a4f4d1a43 100644
--- a/sys/sys/socketvar.h
+++ b/sys/sys/socketvar.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: socketvar.h,v 1.74 2017/07/12 10:56:47 mpi Exp $	*/
+/*	$OpenBSD: socketvar.h,v 1.75 2017/08/22 09:13:36 mpi Exp $	*/
 /*	$NetBSD: socketvar.h,v 1.18 1996/02/09 18:25:38 christos Exp $	*/
 
 /*-
@@ -312,8 +312,7 @@ int	soconnect2(struct socket *so1, struct socket *so2);
 int	socreate(int dom, struct socket **aso, int type, int proto);
 int	sodisconnect(struct socket *so);
 void	sofree(struct socket *so);
-int	sogetopt(struct socket *so, int level, int optname,
-	    struct mbuf **mp);
+int	sogetopt(struct socket *so, int level, int optname, struct mbuf *m);
 void	sohasoutofband(struct socket *so);
 void	soisconnected(struct socket *so);
 void	soisconnecting(struct socket *so);