RDMA/netlink: Fix locking around __ib_get_device_by_index

Holding locks is mandatory when calling __ib_device_get_by_index,
otherwise there are races during the list iteration with device removal.

Since the locks are static to device.c, __ib_device_get_by_index can
never be called correctly by any user out side the file.

Make the function static and provide a safe function that gets the
correct locks and returns a kref'd pointer. Fix all callers.

Fixes: e5c9469e ("RDMA/netlink: Add nldev device doit implementation")
Fixes: c3f66f7b ("RDMA/netlink: Implement nldev port doit callback")
Fixes: 7d02f605 ("RDMA/netlink: Add nldev port dumpit implementation")
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/core_priv.h

@@ -314,7 +314,7 @@ static inline int ib_mad_enforce_security(struct ib_mad_agent_private *map,
 }
 #endif
 
-struct ib_device *__ib_device_get_by_index(u32 ifindex);
+struct ib_device *ib_device_get_by_index(u32 ifindex);
 /* RDMA device netlink */
 void nldev_init(void);
 void nldev_exit(void);

drivers/infiniband/core/device.c

@@ -134,7 +134,7 @@ static int ib_device_check_mandatory(struct ib_device *device)
 	return 0;
 }
 
-struct ib_device *__ib_device_get_by_index(u32 index)
+static struct ib_device *__ib_device_get_by_index(u32 index)
 {
 	struct ib_device *device;
 
@@ -145,6 +145,22 @@ struct ib_device *__ib_device_get_by_index(u32 index)
 	return NULL;
 }
 
+/*
+ * Caller is responsible to return refrerence count by calling put_device()
+ */
+struct ib_device *ib_device_get_by_index(u32 index)
+{
+	struct ib_device *device;
+
+	down_read(&lists_rwsem);
+	device = __ib_device_get_by_index(index);
+	if (device)
+		get_device(&device->dev);
+
+	up_read(&lists_rwsem);
+	return device;
+}
+
 static struct ib_device *__ib_device_get_by_name(const char *name)
 {
 	struct ib_device *device;

drivers/infiniband/core/nldev.c

@@ -142,27 +142,34 @@ static int nldev_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
 
-	device = __ib_device_get_by_index(index);
+	device = ib_device_get_by_index(index);
 	if (!device)
 		return -EINVAL;
 
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-	if (!msg)
-		return -ENOMEM;
+	if (!msg) {
+		err = -ENOMEM;
+		goto err;
+	}
 
 	nlh = nlmsg_put(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq,
 			RDMA_NL_GET_TYPE(RDMA_NL_NLDEV, RDMA_NLDEV_CMD_GET),
 			0, 0);
 
 	err = fill_dev_info(msg, device);
-	if (err) {
-		nlmsg_free(msg);
-		return err;
-	}
+	if (err)
+		goto err_free;
 
 	nlmsg_end(msg, nlh);
 
+	put_device(&device->dev);
 	return rdma_nl_unicast(msg, NETLINK_CB(skb).portid);
+
+err_free:
+	nlmsg_free(msg);
+err:
+	put_device(&device->dev);
+	return err;
 }
 
 static int _nldev_get_dumpit(struct ib_device *device,
@@ -220,31 +227,40 @@ static int nldev_port_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 		return -EINVAL;
 
 	index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
-	device = __ib_device_get_by_index(index);
+	device = ib_device_get_by_index(index);
 	if (!device)
 		return -EINVAL;
 
 	port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
-	if (!rdma_is_port_valid(device, port))
-		return -EINVAL;
+	if (!rdma_is_port_valid(device, port)) {
+		err = -EINVAL;
+		goto err;
+	}
 
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-	if (!msg)
-		return -ENOMEM;
+	if (!msg) {
+		err = -ENOMEM;
+		goto err;
+	}
 
 	nlh = nlmsg_put(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq,
 			RDMA_NL_GET_TYPE(RDMA_NL_NLDEV, RDMA_NLDEV_CMD_GET),
 			0, 0);
 
 	err = fill_port_info(msg, device, port);
-	if (err) {
-		nlmsg_free(msg);
-		return err;
-	}
+	if (err)
+		goto err_free;
 
 	nlmsg_end(msg, nlh);
+	put_device(&device->dev);
 
 	return rdma_nl_unicast(msg, NETLINK_CB(skb).portid);
+
+err_free:
+	nlmsg_free(msg);
+err:
+	put_device(&device->dev);
+	return err;
 }
 
 static int nldev_port_get_dumpit(struct sk_buff *skb,
@@ -265,7 +281,7 @@ static int nldev_port_get_dumpit(struct sk_buff *skb,
 		return -EINVAL;
 
 	ifindex = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
-	device = __ib_device_get_by_index(ifindex);
+	device = ib_device_get_by_index(ifindex);
 	if (!device)
 		return -EINVAL;
 
@@ -299,7 +315,9 @@ static int nldev_port_get_dumpit(struct sk_buff *skb,
 		nlmsg_end(skb, nlh);
 	}
 
-out:	cb->args[0] = idx;
+out:
+	put_device(&device->dev);
+	cb->args[0] = idx;
 	return skb->len;
 }