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
|
// Copyright 2019 The gVisor Authors.
//
// 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 ext implements readonly ext(2/3/4) filesystems.
package ext
import (
"errors"
"fmt"
"io"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
)
// Name is the name of this filesystem.
const Name = "ext"
// FilesystemType implements vfs.FilesystemType.
//
// +stateify savable
type FilesystemType struct{}
// Compiles only if FilesystemType implements vfs.FilesystemType.
var _ vfs.FilesystemType = (*FilesystemType)(nil)
// getDeviceFd returns an io.ReaderAt to the underlying device.
// Currently there are two ways of mounting an ext(2/3/4) fs:
// 1. Specify a mount with our internal special MountType in the OCI spec.
// 2. Expose the device to the container and mount it from application layer.
func getDeviceFd(source string, opts vfs.GetFilesystemOptions) (io.ReaderAt, error) {
if opts.InternalData == nil {
// User mount call.
// TODO(b/134676337): Open the device specified by `source` and return that.
panic("unimplemented")
}
// GetFilesystem call originated from within the sentry.
devFd, ok := opts.InternalData.(int)
if !ok {
return nil, errors.New("internal data for ext fs must be an int containing the file descriptor to device")
}
if devFd < 0 {
return nil, fmt.Errorf("ext device file descriptor is not valid: %d", devFd)
}
// The fd.ReadWriter returned from fd.NewReadWriter() does not take ownership
// of the file descriptor and hence will not close it when it is garbage
// collected.
return fd.NewReadWriter(devFd), nil
}
// isCompatible checks if the superblock has feature sets which are compatible.
// We only need to check the superblock incompatible feature set since we are
// mounting readonly. We will also need to check readonly compatible feature
// set when mounting for read/write.
func isCompatible(sb disklayout.SuperBlock) bool {
// Please note that what is being checked is limited based on the fact that we
// are mounting readonly and that we are not journaling. When mounting
// read/write or with a journal, this must be reevaluated.
incompatFeatures := sb.IncompatibleFeatures()
if incompatFeatures.MetaBG {
log.Warningf("ext fs: meta block groups are not supported")
return false
}
if incompatFeatures.MMP {
log.Warningf("ext fs: multiple mount protection is not supported")
return false
}
if incompatFeatures.Encrypted {
log.Warningf("ext fs: encrypted inodes not supported")
return false
}
if incompatFeatures.InlineData {
log.Warningf("ext fs: inline files not supported")
return false
}
return true
}
// Name implements vfs.FilesystemType.Name.
func (FilesystemType) Name() string {
return Name
}
// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
func (fsType FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
// TODO(b/134676337): Ensure that the user is mounting readonly. If not,
// EACCESS should be returned according to mount(2). Filesystem independent
// flags (like readonly) are currently not available in pkg/sentry/vfs.
devMinor, err := vfsObj.GetAnonBlockDevMinor()
if err != nil {
return nil, nil, err
}
dev, err := getDeviceFd(source, opts)
if err != nil {
return nil, nil, err
}
fs := filesystem{
dev: dev,
inodeCache: make(map[uint32]*inode),
devMinor: devMinor,
}
fs.vfsfs.Init(vfsObj, &fsType, &fs)
fs.sb, err = readSuperBlock(dev)
if err != nil {
fs.vfsfs.DecRef(ctx)
return nil, nil, err
}
if fs.sb.Magic() != linux.EXT_SUPER_MAGIC {
// mount(2) specifies that EINVAL should be returned if the superblock is
// invalid.
fs.vfsfs.DecRef(ctx)
return nil, nil, syserror.EINVAL
}
// Refuse to mount if the filesystem is incompatible.
if !isCompatible(fs.sb) {
fs.vfsfs.DecRef(ctx)
return nil, nil, syserror.EINVAL
}
fs.bgs, err = readBlockGroups(dev, fs.sb)
if err != nil {
fs.vfsfs.DecRef(ctx)
return nil, nil, err
}
rootInode, err := fs.getOrCreateInodeLocked(disklayout.RootDirInode)
if err != nil {
fs.vfsfs.DecRef(ctx)
return nil, nil, err
}
rootInode.incRef()
return &fs.vfsfs, &newDentry(rootInode).vfsd, nil
}
|
