SUNRPC: Do not dereference non-socket transports in sysfs

Do not cast the struct xprt to a sock_xprt unless we know it is a UDP or
TCP transport. Otherwise the call to lock the mutex will scribble over
whatever structure is actually there. This has been seen to cause hard
system lockups when the underlying transport was RDMA.

Fixes: b49ea673 ("SUNRPC: lock against ->sock changing during sysfs read")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/xprt.h

@@ -139,6 +139,9 @@ struct rpc_xprt_ops {
 	void		(*rpcbind)(struct rpc_task *task);
 	void		(*set_port)(struct rpc_xprt *xprt, unsigned short port);
 	void		(*connect)(struct rpc_xprt *xprt, struct rpc_task *task);
+	int		(*get_srcaddr)(struct rpc_xprt *xprt, char *buf,
+				       size_t buflen);
+	unsigned short	(*get_srcport)(struct rpc_xprt *xprt);
 	int		(*buf_alloc)(struct rpc_task *task);
 	void		(*buf_free)(struct rpc_task *task);
 	void		(*prepare_request)(struct rpc_rqst *req);

include/linux/sunrpc/xprtsock.h

@@ -10,7 +10,6 @@
 
 int		init_socket_xprt(void);
 void		cleanup_socket_xprt(void);
-unsigned short	get_srcport(struct rpc_xprt *);
 
 #define RPC_MIN_RESVPORT	(1U)
 #define RPC_MAX_RESVPORT	(65535U)

net/sunrpc/sysfs.c

@@ -97,7 +97,7 @@ static ssize_t rpc_sysfs_xprt_dstaddr_show(struct kobject *kobj,
 		return 0;
 	ret = sprintf(buf, "%s\n", xprt->address_strings[RPC_DISPLAY_ADDR]);
 	xprt_put(xprt);
-	return ret + 1;
+	return ret;
 }
 
 static ssize_t rpc_sysfs_xprt_srcaddr_show(struct kobject *kobj,
@@ -105,33 +105,31 @@ static ssize_t rpc_sysfs_xprt_srcaddr_show(struct kobject *kobj,
 					   char *buf)
 {
 	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
-	struct sockaddr_storage saddr;
-	struct sock_xprt *sock;
-	ssize_t ret = -1;
+	size_t buflen = PAGE_SIZE;
+	ssize_t ret = -ENOTSOCK;
 
 	if (!xprt || !xprt_connected(xprt)) {
-		xprt_put(xprt);
-		return -ENOTCONN;
+		ret = -ENOTCONN;
+	} else if (xprt->ops->get_srcaddr) {
+		ret = xprt->ops->get_srcaddr(xprt, buf, buflen);
+		if (ret > 0) {
+			if (ret < buflen - 1) {
+				buf[ret] = '\n';
+				ret++;
+				buf[ret] = '\0';
+			}
+		}
 	}
-
-	sock = container_of(xprt, struct sock_xprt, xprt);
-	mutex_lock(&sock->recv_mutex);
-	if (sock->sock == NULL ||
-	    kernel_getsockname(sock->sock, (struct sockaddr *)&saddr) < 0)
-		goto out;
-
-	ret = sprintf(buf, "%pISc\n", &saddr);
-out:
-	mutex_unlock(&sock->recv_mutex);
 	xprt_put(xprt);
-	return ret + 1;
+	return ret;
 }
 
 static ssize_t rpc_sysfs_xprt_info_show(struct kobject *kobj,
-					struct kobj_attribute *attr,
-					char *buf)
+					struct kobj_attribute *attr, char *buf)
 {
 	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	unsigned short srcport = 0;
+	size_t buflen = PAGE_SIZE;
 	ssize_t ret;
 
 	if (!xprt || !xprt_connected(xprt)) {
@@ -139,7 +137,11 @@ static ssize_t rpc_sysfs_xprt_info_show(struct kobject *kobj,
 		return -ENOTCONN;
 	}
 
-	ret = sprintf(buf, "last_used=%lu\ncur_cong=%lu\ncong_win=%lu\n"
+	if (xprt->ops->get_srcport)
+		srcport = xprt->ops->get_srcport(xprt);
+
+	ret = snprintf(buf, buflen,
+		       "last_used=%lu\ncur_cong=%lu\ncong_win=%lu\n"
 		       "max_num_slots=%u\nmin_num_slots=%u\nnum_reqs=%u\n"
 		       "binding_q_len=%u\nsending_q_len=%u\npending_q_len=%u\n"
 		       "backlog_q_len=%u\nmain_xprt=%d\nsrc_port=%u\n"
@@ -147,14 +149,11 @@ static ssize_t rpc_sysfs_xprt_info_show(struct kobject *kobj,
 		       xprt->last_used, xprt->cong, xprt->cwnd, xprt->max_reqs,
 		       xprt->min_reqs, xprt->num_reqs, xprt->binding.qlen,
 		       xprt->sending.qlen, xprt->pending.qlen,
-		       xprt->backlog.qlen, xprt->main,
-		       (xprt->xprt_class->ident == XPRT_TRANSPORT_TCP) ?
-		       get_srcport(xprt) : 0,
+		       xprt->backlog.qlen, xprt->main, srcport,
 		       atomic_long_read(&xprt->queuelen),
-		       (xprt->xprt_class->ident == XPRT_TRANSPORT_TCP) ?
-				xprt->address_strings[RPC_DISPLAY_PORT] : "0");
+		       xprt->address_strings[RPC_DISPLAY_PORT]);
 	xprt_put(xprt);
-	return ret + 1;
+	return ret;
 }
 
 static ssize_t rpc_sysfs_xprt_state_show(struct kobject *kobj,
@@ -201,7 +200,7 @@ static ssize_t rpc_sysfs_xprt_state_show(struct kobject *kobj,
 	}
 
 	xprt_put(xprt);
-	return ret + 1;
+	return ret;
 }
 
 static ssize_t rpc_sysfs_xprt_switch_info_show(struct kobject *kobj,
@@ -220,7 +219,7 @@ static ssize_t rpc_sysfs_xprt_switch_info_show(struct kobject *kobj,
 		      xprt_switch->xps_nunique_destaddr_xprts,
 		      atomic_long_read(&xprt_switch->xps_queuelen));
 	xprt_switch_put(xprt_switch);
-	return ret + 1;
+	return ret;
 }
 
 static ssize_t rpc_sysfs_xprt_dstaddr_store(struct kobject *kobj,

net/sunrpc/xprtsock.c

@@ -1638,7 +1638,7 @@ static int xs_get_srcport(struct sock_xprt *transport)
 	return port;
 }
 
-unsigned short get_srcport(struct rpc_xprt *xprt)
+static unsigned short xs_sock_srcport(struct rpc_xprt *xprt)
 {
 	struct sock_xprt *sock = container_of(xprt, struct sock_xprt, xprt);
 	unsigned short ret = 0;
@@ -1648,7 +1648,25 @@ unsigned short get_srcport(struct rpc_xprt *xprt)
 	mutex_unlock(&sock->recv_mutex);
 	return ret;
 }
-EXPORT_SYMBOL(get_srcport);
+
+static int xs_sock_srcaddr(struct rpc_xprt *xprt, char *buf, size_t buflen)
+{
+	struct sock_xprt *sock = container_of(xprt, struct sock_xprt, xprt);
+	union {
+		struct sockaddr sa;
+		struct sockaddr_storage st;
+	} saddr;
+	int ret = -ENOTCONN;
+
+	mutex_lock(&sock->recv_mutex);
+	if (sock->sock) {
+		ret = kernel_getsockname(sock->sock, &saddr.sa);
+		if (ret >= 0)
+			ret = snprintf(buf, buflen, "%pISc", &saddr.sa);
+	}
+	mutex_unlock(&sock->recv_mutex);
+	return ret;
+}
 
 static unsigned short xs_next_srcport(struct sock_xprt *transport, unsigned short port)
 {
@@ -2622,6 +2640,8 @@ static const struct rpc_xprt_ops xs_udp_ops = {
 	.rpcbind		= rpcb_getport_async,
 	.set_port		= xs_set_port,
 	.connect		= xs_connect,
+	.get_srcaddr		= xs_sock_srcaddr,
+	.get_srcport		= xs_sock_srcport,
 	.buf_alloc		= rpc_malloc,
 	.buf_free		= rpc_free,
 	.send_request		= xs_udp_send_request,
@@ -2644,6 +2664,8 @@ static const struct rpc_xprt_ops xs_tcp_ops = {
 	.rpcbind		= rpcb_getport_async,
 	.set_port		= xs_set_port,
 	.connect		= xs_connect,
+	.get_srcaddr		= xs_sock_srcaddr,
+	.get_srcport		= xs_sock_srcport,
 	.buf_alloc		= rpc_malloc,
 	.buf_free		= rpc_free,
 	.prepare_request	= xs_stream_prepare_request,