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
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
// +build linux
package overlay
import (
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"syscall"
"github.com/containers/storage/pkg/ioutils"
"github.com/containers/storage/pkg/mount"
"github.com/containers/storage/pkg/system"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"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.
func doesSupportNativeDiff(d, mountOpts string) error {
td, err := ioutil.TempDir(d, "opaque-bug-check")
if err != nil {
return err
}
defer func() {
if err := os.RemoveAll(td); err != nil {
logrus.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, "work"), 0755); err != nil {
return err
}
if err := os.Mkdir(filepath.Join(td, "merged"), 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, "work"))
flags, data := mount.ParseOptions(mountOpts)
if data != "" {
opts = fmt.Sprintf("%s,%s", opts, data)
}
if err := unix.Mount("overlay", filepath.Join(td, "merged"), "overlay", uintptr(flags), opts); err != nil {
return errors.Wrap(err, "failed to mount overlay")
}
defer func() {
if err := unix.Unmount(filepath.Join(td, "merged"), 0); err != nil {
logrus.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
}
}()
// Touch file in d to force copy up of opaque directory "d" from "l2" to "l3"
if err := ioutil.WriteFile(filepath.Join(td, "merged", "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, "merged", "d1"), filepath.Join(td, "merged", "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
}
// doesMetacopy checks if the filesystem is going to optimize changes to
// metadata by using nodes marked with an "overlay.metacopy" attribute to avoid
// copying up a file from a lower layer unless/until its contents are being
// modified
func doesMetacopy(d, mountOpts string) (bool, error) {
td, err := ioutil.TempDir(d, "metacopy-check")
if err != nil {
return false, err
}
defer func() {
if err := os.RemoveAll(td); err != nil {
logrus.Warnf("Failed to remove check directory %v: %v", td, err)
}
}()
// Make directories l1, l2, work, merged
if err := os.MkdirAll(filepath.Join(td, "l1"), 0755); err != nil {
return false, err
}
if err := ioutils.AtomicWriteFile(filepath.Join(td, "l1", "f"), []byte{0xff}, 0700); err != nil {
return false, err
}
if err := os.MkdirAll(filepath.Join(td, "l2"), 0755); err != nil {
return false, err
}
if err := os.Mkdir(filepath.Join(td, "work"), 0755); err != nil {
return false, err
}
if err := os.Mkdir(filepath.Join(td, "merged"), 0755); err != nil {
return false, err
}
// Mount using the mandatory options and configured options
opts := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", path.Join(td, "l1"), path.Join(td, "l2"), path.Join(td, "work"))
flags, data := mount.ParseOptions(mountOpts)
if data != "" {
opts = fmt.Sprintf("%s,%s", opts, data)
}
if err := unix.Mount("overlay", filepath.Join(td, "merged"), "overlay", uintptr(flags), opts); err != nil {
if errors.Cause(err) == unix.EINVAL {
logrus.Info("metacopy option not supported on this kernel", mountOpts)
return false, nil
}
return false, errors.Wrapf(err, "failed to mount overlay for metacopy check with %q options", mountOpts)
}
defer func() {
if err := unix.Unmount(filepath.Join(td, "merged"), 0); err != nil {
logrus.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
}
}()
// Make a change that only impacts the inode, and check if the pulled-up copy is marked
// as a metadata-only copy
if err := os.Chmod(filepath.Join(td, "merged", "f"), 0600); err != nil {
return false, errors.Wrap(err, "error changing permissions on file for metacopy check")
}
metacopy, err := system.Lgetxattr(filepath.Join(td, "l2", "f"), "trusted.overlay.metacopy")
if err != nil {
return false, errors.Wrap(err, "metacopy flag was not set on file in upper layer")
}
return metacopy != nil, nil
}
|
