Fail to start server if detected cross-device mounts. (#4807)

Fixes #4764

cmd/endpoint.go

@@ -21,11 +21,13 @@ import (
 	"net"
 	"net/url"
 	"path"
+	"path/filepath"
 	"sort"
 	"strconv"
 	"strings"
 
 	"github.com/minio/minio-go/pkg/set"
+	"github.com/minio/minio/pkg/mountinfo"
 )
 
 // EndpointType - enum for endpoint type.
@@ -99,7 +101,8 @@ func NewEndpoint(arg string) (ep Endpoint, e error) {
 			return ep, fmt.Errorf("invalid URL endpoint format")
 		}
 
-		host, port, err := net.SplitHostPort(u.Host)
+		var host, port string
+		host, port, err = net.SplitHostPort(u.Host)
 		if err != nil {
 			if !strings.Contains(err.Error(), "missing port in address") {
 				return ep, fmt.Errorf("invalid URL endpoint format: %s", err)
@@ -226,6 +229,22 @@ func NewEndpointList(args ...string) (endpoints EndpointList, err error) {
 	return endpoints, nil
 }
 
+// Checks if there are any cross device mounts.
+func checkCrossDeviceMounts(endpoints EndpointList) (err error) {
+	var absPaths []string
+	for _, endpoint := range endpoints {
+		if endpoint.IsLocal {
+			var absPath string
+			absPath, err = filepath.Abs(endpoint.Path)
+			if err != nil {
+				return err
+			}
+			absPaths = append(absPaths, absPath)
+		}
+	}
+	return mountinfo.CheckCrossDevice(absPaths)
+}
+
 // CreateEndpoints - validates and creates new endpoints for given args.
 func CreateEndpoints(serverAddr string, args ...string) (string, EndpointList, SetupType, error) {
 	var endpoints EndpointList
@@ -246,13 +265,16 @@ func CreateEndpoints(serverAddr string, args ...string) (string, EndpointList, S
 		if err != nil {
 			return serverAddr, endpoints, setupType, err
 		}
-
 		if endpoint.Type() != PathEndpointType {
 			return serverAddr, endpoints, setupType, fmt.Errorf("use path style endpoint for FS setup")
 		}
-
 		endpoints = append(endpoints, endpoint)
 		setupType = FSSetupType
+
+		// Check for cross device mounts if any.
+		if err = checkCrossDeviceMounts(endpoints); err != nil {
+			return serverAddr, endpoints, setupType, err
+		}
 		return serverAddr, endpoints, setupType, nil
 	}
 
@@ -261,6 +283,11 @@ func CreateEndpoints(serverAddr string, args ...string) (string, EndpointList, S
 		return serverAddr, endpoints, setupType, err
 	}
 
+	// Check for cross device mounts if any.
+	if err = checkCrossDeviceMounts(endpoints); err != nil {
+		return serverAddr, endpoints, setupType, err
+	}
+
 	// Return XL setup when all endpoints are path style.
 	if endpoints[0].Type() == PathEndpointType {
 		setupType = XLSetupType