2017-08-16 00:10:50 +02:00
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// +build linux
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/*
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2018-06-28 03:59:38 +02:00
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* Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
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2017-08-16 00:10:50 +02:00
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package mountinfo
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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2018-06-28 03:59:38 +02:00
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"syscall"
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2017-08-16 00:10:50 +02:00
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)
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const (
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// Number of fields per line in /proc/mounts as per the fstab man page.
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expectedNumFieldsPerLine = 6
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// Location of the mount file to use
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procMountsPath = "/proc/mounts"
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)
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2018-06-28 03:59:38 +02:00
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// IsLikelyMountPoint determines if a directory is a mountpoint.
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// It is fast but not necessarily ALWAYS correct. If the path is in fact
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// a bind mount from one part of a mount to another it will not be detected.
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// mkdir /tmp/a /tmp/b; mount --bin /tmp/a /tmp/b; IsLikelyMountPoint("/tmp/b")
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// will return false. When in fact /tmp/b is a mount point. If this situation
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// if of interest to you, don't use this function...
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func IsLikelyMountPoint(file string) bool {
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stat, err := os.Stat(file)
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if err != nil {
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return false
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}
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rootStat, err := os.Lstat(filepath.Dir(strings.TrimSuffix(file, "/")))
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if err != nil {
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return false
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}
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// If the directory has a different device as parent, then it is a mountpoint.
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return stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev
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}
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2017-08-16 00:10:50 +02:00
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// CheckCrossDevice - check if any list of paths has any sub-mounts at /proc/mounts.
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func CheckCrossDevice(absPaths []string) error {
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return checkCrossDevice(absPaths, procMountsPath)
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}
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// Check cross device is an internal function.
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func checkCrossDevice(absPaths []string, mountsPath string) error {
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mounts, err := readProcMounts(mountsPath)
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if err != nil {
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return err
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}
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for _, path := range absPaths {
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if err := mounts.checkCrossMounts(path); err != nil {
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return err
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}
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}
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return nil
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}
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// CheckCrossDevice - check if given path has any sub-mounts in the input mounts list.
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func (mts mountInfos) checkCrossMounts(path string) error {
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if !filepath.IsAbs(path) {
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return fmt.Errorf("Invalid argument, path (%s) is expected to be absolute", path)
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}
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var crossMounts mountInfos
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for _, mount := range mts {
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// Add a separator to indicate that this is a proper mount-point.
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// This is to avoid a situation where prefix is '/tmp/fsmount'
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// and mount path is /tmp/fs. In such a scenario we need to check for
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// `/tmp/fs/` to be a common prefix amount other mounts.
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mpath := strings.TrimSuffix(mount.Path, "/") + "/"
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ppath := strings.TrimSuffix(path, "/") + "/"
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if strings.HasPrefix(mpath, ppath) {
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// At this point if the mount point has a common prefix two conditions can happen.
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// - mount.Path matches exact with `path` means we can proceed no error here.
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// - mount.Path doesn't match (means cross-device mount), should error out.
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if mount.Path != path {
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crossMounts = append(crossMounts, mount)
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}
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}
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}
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msg := `Cross-device mounts detected on path (%s) at following locations %s. Export path should not have any sub-mounts, refusing to start.`
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if len(crossMounts) > 0 {
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// if paths didn't match then we do have cross-device mount.
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return fmt.Errorf(msg, path, crossMounts)
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}
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return nil
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}
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// readProcMounts reads the given mountFilePath (normally /proc/mounts) and produces a hash
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// of the contents. If the out argument is not nil, this fills it with MountPoint structs.
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func readProcMounts(mountFilePath string) (mountInfos, error) {
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file, err := os.Open(mountFilePath)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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return parseMountFrom(file)
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}
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func parseMountFrom(file io.Reader) (mountInfos, error) {
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var mounts = mountInfos{}
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scanner := bufio.NewReader(file)
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for {
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line, err := scanner.ReadString('\n')
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if err == io.EOF {
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break
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}
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fields := strings.Fields(line)
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if len(fields) != expectedNumFieldsPerLine {
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return nil, fmt.Errorf("wrong number of fields (expected %d, got %d): %s", expectedNumFieldsPerLine, len(fields), line)
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}
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// Freq should be an integer.
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if _, err := strconv.Atoi(fields[4]); err != nil {
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return nil, err
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}
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// Pass should be an integer.
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if _, err := strconv.Atoi(fields[5]); err != nil {
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return nil, err
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}
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mounts = append(mounts, mountInfo{
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Device: fields[0],
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Path: fields[1],
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FSType: fields[2],
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Options: strings.Split(fields[3], ","),
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Freq: fields[4],
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Pass: fields[5],
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})
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}
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return mounts, nil
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}
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