reject mixed drive situations with drives on root disks (#11057)

till now we used to match the inode number of the root
drive and the drive path minio would use, if they match
we knew that its a root disk.

this may not be true in all situations such as running
inside a container environment where the container might
be mounted from a different partition altogether, root
disk detection might fail.

cmd/xl-storage.go

@@ -240,7 +240,7 @@ func newXLStorage(ep Endpoint) (*xlStorage, error) {
 		return nil, err
 	}
 
-	rootDisk, err := disk.IsRootDisk(path)
+	rootDisk, err := disk.IsRootDisk(path, "/")
 	if err != nil {
 		return nil, err
 	}

pkg/disk/disk.go

@@ -30,3 +30,21 @@ type Info struct {
 	Ffree  uint64
 	FSType string
 }
+
+// SameDisk reports whether di1 and di2 describe the same disk.
+func SameDisk(di1, di2 Info) bool {
+	if di1.Total != di2.Total {
+		// disk total size different
+		return false
+	}
+
+	if di1.Files != di2.Files {
+		// disk total inodes different
+		return false
+	}
+
+	// returns true only if Used, Free and number of free
+	// inodes are same, then its the same disk.
+	return di1.Used == di2.Used && di1.Free == di2.Free &&
+		di1.Ffree == di2.Ffree
+}

pkg/disk/root_disk.go

@@ -1,7 +1,5 @@
-// +build windows
-
 /*
- * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,8 +17,21 @@
 
 package disk
 
+import "runtime"
+
 // IsRootDisk returns if diskPath belongs to root-disk, i.e the disk mounted at "/"
-func IsRootDisk(diskPath string) (bool, error) {
-	// On windows a disk can never be mounted on a subpath.
-	return false, nil
+func IsRootDisk(diskPath string, rootDisk string) (bool, error) {
+	if runtime.GOOS == "windows" {
+		// On windows this function is not implemented.
+		return false, nil
+	}
+	info, err := GetInfo(diskPath)
+	if err != nil {
+		return false, err
+	}
+	rootInfo, err := GetInfo(rootDisk)
+	if err != nil {
+		return false, err
+	}
+	return SameDisk(info, rootInfo), nil
 }

pkg/disk/root_disk_unix.go

@@ -1,62 +0,0 @@
-// +build !windows
-
-/*
- * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-package disk
-
-import (
-	"os"
-	"syscall"
-)
-
-// IsRootDisk returns if diskPath belongs to root-disk, i.e the disk mounted at "/"
-func IsRootDisk(diskPath string) (bool, error) {
-	rootDisk := false
-	diskInfo, err := os.Stat(diskPath)
-	if err != nil {
-		return false, err
-	}
-	rootHostsInfo, err := os.Stat("/etc/hosts")
-	if err != nil {
-		return false, err
-	}
-	rootInfo, err := os.Stat("/")
-	if err != nil {
-		return false, err
-	}
-	diskStat, diskStatOK := diskInfo.Sys().(*syscall.Stat_t)
-	rootHostsStat, rootHostsStatOK := rootHostsInfo.Sys().(*syscall.Stat_t)
-	rootStat, rootStatOK := rootInfo.Sys().(*syscall.Stat_t)
-	if diskStatOK && rootHostsStatOK {
-		if diskStat.Dev == rootHostsStat.Dev {
-			// Indicate if the disk path is on root disk. This is used to indicate the healing
-			// process not to format the drive and end up healing it.
-			rootDisk = true
-		}
-	}
-	if !rootDisk {
-		if diskStatOK && rootStatOK {
-			if diskStat.Dev == rootStat.Dev {
-				// Indicate if the disk path is on root disk. This is used to indicate the healing
-				// process not to format the drive and end up healing it.
-				rootDisk = true
-			}
-		}
-	}
-	return rootDisk, nil
-}