1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
//go:build linux
// +build linux
package overlay2 // import "github.com/docker/docker/daemon/graphdriver/overlay2"
import (
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"syscall"
"github.com/containerd/containerd/sys"
"github.com/docker/docker/pkg/system"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
)
// doesSupportNativeDiff checks whether the filesystem has a bug
// which copies up the opaque flag when copying up an opaque
// directory or the kernel enable CONFIG_OVERLAY_FS_REDIRECT_DIR.
// When these exist naive diff should be used.
//
// When running in a user namespace, returns errRunningInUserNS
// immediately.
func doesSupportNativeDiff(d string) error {
if sys.RunningInUserNS() {
return errors.New("running in a user namespace")
}
td, err := ioutil.TempDir(d, "opaque-bug-check")
if err != nil {
return err
}
defer func() {
if err := os.RemoveAll(td); err != nil {
logger.Warnf("Failed to remove check directory %v: %v", td, err)
}
}()
// Make directories l1/d, l1/d1, l2/d, l3, work, merged
if err := os.MkdirAll(filepath.Join(td, "l1", "d"), 0755); err != nil {
return err
}
if err := os.MkdirAll(filepath.Join(td, "l1", "d1"), 0755); err != nil {
return err
}
if err := os.MkdirAll(filepath.Join(td, "l2", "d"), 0755); err != nil {
return err
}
if err := os.Mkdir(filepath.Join(td, "l3"), 0755); err != nil {
return err
}
if err := os.Mkdir(filepath.Join(td, workDirName), 0755); err != nil {
return err
}
if err := os.Mkdir(filepath.Join(td, mergedDirName), 0755); err != nil {
return err
}
// Mark l2/d as opaque
if err := system.Lsetxattr(filepath.Join(td, "l2", "d"), "trusted.overlay.opaque", []byte("y"), 0); err != nil {
return errors.Wrap(err, "failed to set opaque flag on middle layer")
}
opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "l2"), path.Join(td, "l1"), path.Join(td, "l3"), path.Join(td, workDirName))
if err := unix.Mount("overlay", filepath.Join(td, mergedDirName), "overlay", 0, opts); err != nil {
return errors.Wrap(err, "failed to mount overlay")
}
defer func() {
if err := unix.Unmount(filepath.Join(td, mergedDirName), 0); err != nil {
logger.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, mergedDirName), err)
}
}()
// Touch file in d to force copy up of opaque directory "d" from "l2" to "l3"
if err := ioutil.WriteFile(filepath.Join(td, mergedDirName, "d", "f"), []byte{}, 0644); err != nil {
return errors.Wrap(err, "failed to write to merged directory")
}
// Check l3/d does not have opaque flag
xattrOpaque, err := system.Lgetxattr(filepath.Join(td, "l3", "d"), "trusted.overlay.opaque")
if err != nil {
return errors.Wrap(err, "failed to read opaque flag on upper layer")
}
if string(xattrOpaque) == "y" {
return errors.New("opaque flag erroneously copied up, consider update to kernel 4.8 or later to fix")
}
// rename "d1" to "d2"
if err := os.Rename(filepath.Join(td, mergedDirName, "d1"), filepath.Join(td, mergedDirName, "d2")); err != nil {
// if rename failed with syscall.EXDEV, the kernel doesn't have CONFIG_OVERLAY_FS_REDIRECT_DIR enabled
if err.(*os.LinkError).Err == syscall.EXDEV {
return nil
}
return errors.Wrap(err, "failed to rename dir in merged directory")
}
// get the xattr of "d2"
xattrRedirect, err := system.Lgetxattr(filepath.Join(td, "l3", "d2"), "trusted.overlay.redirect")
if err != nil {
return errors.Wrap(err, "failed to read redirect flag on upper layer")
}
if string(xattrRedirect) == "d1" {
return errors.New("kernel has CONFIG_OVERLAY_FS_REDIRECT_DIR enabled")
}
return nil
}
|
