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
170
171
|
// +build linux
package syscallcompat
// Other implementations of getdents in Go:
// https://github.com/ericlagergren/go-gnulib/blob/cb7a6e136427e242099b2c29d661016c19458801/dirent/getdents_unix.go
// https://github.com/golang/tools/blob/5831d16d18029819d39f99bdc2060b8eff410b6b/imports/fastwalk_unix.go
import (
"bytes"
"sync"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
)
const sizeofDirent = int(unsafe.Sizeof(unix.Dirent{}))
// maxReclen sanity check: Reclen should never be larger than this.
// Due to padding between entries, it is 280 even on 32-bit architectures.
// See https://github.com/rfjakob/gocryptfs/issues/197 for details.
const maxReclen = 280
// getdents wraps unix.Getdents and converts the result to []fuse.DirEntry.
func getdents(fd int) (entries []fuse.DirEntry, entriesSpecial []fuse.DirEntry, err error) {
// Collect syscall result in smartBuf.
// "bytes.Buffer" is smart about expanding the capacity and avoids the
// exponential runtime of simple append().
var smartBuf bytes.Buffer
tmp := make([]byte, 10000)
for {
n, err := unix.Getdents(fd, tmp)
// unix.Getdents has been observed to return EINTR on cifs mounts
if err == unix.EINTR {
if n > 0 {
smartBuf.Write(tmp[:n])
}
continue
} else if err != nil {
if smartBuf.Len() > 0 {
tlog.Warn.Printf("warning: unix.Getdents returned errno %d in the middle of data ( https://github.com/rfjakob/gocryptfs/issues/483 )", err.(syscall.Errno))
return nil, nil, syscall.EIO
}
return nil, nil, err
}
if n == 0 {
break
}
smartBuf.Write(tmp[:n])
}
// Make sure we have at least Sizeof(Dirent) of zeros after the last
// entry. This prevents a cast to Dirent from reading past the buffer.
smartBuf.Grow(sizeofDirent)
buf := smartBuf.Bytes()
// Count the number of directory entries in the buffer so we can allocate
// a fuse.DirEntry slice of the correct size at once.
var numEntries, offset int
for offset < len(buf) {
s := *(*unix.Dirent)(unsafe.Pointer(&buf[offset]))
if s.Reclen == 0 {
tlog.Warn.Printf("Getdents: corrupt entry #%d: Reclen=0 at offset=%d. Returning EBADR",
numEntries, offset)
// EBADR = Invalid request descriptor
return nil, nil, syscall.EBADR
}
if int(s.Reclen) > maxReclen {
tlog.Warn.Printf("Getdents: corrupt entry #%d: Reclen=%d > %d. Returning EBADR",
numEntries, s.Reclen, maxReclen)
return nil, nil, syscall.EBADR
}
offset += int(s.Reclen)
numEntries++
}
// Parse the buffer into entries.
// Note: syscall.ParseDirent() only returns the names,
// we want all the data, so we have to implement
// it on our own.
entries = make([]fuse.DirEntry, 0, numEntries)
offset = 0
for offset < len(buf) {
s := *(*unix.Dirent)(unsafe.Pointer(&buf[offset]))
name, err := getdentsName(s)
if err != nil {
return nil, nil, err
}
offset += int(s.Reclen)
if name == "." || name == ".." {
// These are always directories, no need to call convertDType.
entriesSpecial = append(entriesSpecial, fuse.DirEntry{
Ino: s.Ino,
Mode: syscall.S_IFDIR,
Name: name,
})
continue
}
mode, err := convertDType(fd, name, s.Type)
if err != nil {
// The file may have been deleted in the meantime. Just skip it
// and go on.
continue
}
entries = append(entries, fuse.DirEntry{
Ino: s.Ino,
Mode: mode,
Name: name,
})
}
return entries, entriesSpecial, nil
}
// getdentsName extracts the filename from a Dirent struct and returns it as
// a Go string.
func getdentsName(s unix.Dirent) (string, error) {
// After the loop, l contains the index of the first '\0'.
l := 0
for l = range s.Name {
if s.Name[l] == 0 {
break
}
}
if l < 1 {
tlog.Warn.Printf("Getdents: invalid name length l=%d. Returning EBADR", l)
// EBADR = Invalid request descriptor
return "", syscall.EBADR
}
// Copy to byte slice.
name := make([]byte, l)
for i := range name {
name[i] = byte(s.Name[i])
}
return string(name), nil
}
var dtUnknownWarnOnce sync.Once
func dtUnknownWarn(dirfd int) {
const XFS_SUPER_MAGIC = 0x58465342 // From man 2 statfs
var buf syscall.Statfs_t
err := syscall.Fstatfs(dirfd, &buf)
if err == nil && buf.Type == XFS_SUPER_MAGIC {
// Old XFS filesystems always return DT_UNKNOWN. Downgrade the message
// to "info" level if we are on XFS.
// https://github.com/rfjakob/gocryptfs/issues/267
tlog.Info.Printf("Getdents: convertDType: received DT_UNKNOWN, fstype=xfs, falling back to stat")
} else {
tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, fstype=%#x, falling back to stat",
buf.Type)
}
}
// convertDType converts a Dirent.Type to at Stat_t.Mode value.
func convertDType(dirfd int, name string, dtype uint8) (uint32, error) {
if dtype != syscall.DT_UNKNOWN {
// Shift up by four octal digits = 12 bits
return uint32(dtype) << 12, nil
}
// DT_UNKNOWN: we have to call stat()
dtUnknownWarnOnce.Do(func() { dtUnknownWarn(dirfd) })
var st unix.Stat_t
err := Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
return 0, err
}
// The S_IFMT bit mask extracts the file type from the mode.
return st.Mode & syscall.S_IFMT, nil
}
|
