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
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
// Copyright 2018 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 proc
import (
"bytes"
"fmt"
"io"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/usermem"
"gvisor.dev/gvisor/pkg/waiter"
)
// LINT.IfChange
// execArgType enumerates the types of exec arguments that are exposed through
// proc.
type execArgType int
const (
cmdlineExecArg execArgType = iota
environExecArg
)
// execArgInode is a inode containing the exec args (either cmdline or environ)
// for a given task.
//
// +stateify savable
type execArgInode struct {
fsutil.SimpleFileInode
// arg is the type of exec argument this file contains.
arg execArgType
// t is the Task to read the exec arg line from.
t *kernel.Task
}
var _ fs.InodeOperations = (*execArgInode)(nil)
// newExecArgFile creates a file containing the exec args of the given type.
func newExecArgInode(ctx context.Context, t *kernel.Task, msrc *fs.MountSource, arg execArgType) *fs.Inode {
if arg != cmdlineExecArg && arg != environExecArg {
panic(fmt.Sprintf("unknown exec arg type %v", arg))
}
f := &execArgInode{
SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
arg: arg,
t: t,
}
return newProcInode(ctx, f, msrc, fs.SpecialFile, t)
}
// GetFile implements fs.InodeOperations.GetFile.
func (i *execArgInode) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
return fs.NewFile(ctx, dirent, flags, &execArgFile{
arg: i.arg,
t: i.t,
}), nil
}
// +stateify savable
type execArgFile struct {
fsutil.FileGenericSeek `state:"nosave"`
fsutil.FileNoIoctl `state:"nosave"`
fsutil.FileNoMMap `state:"nosave"`
fsutil.FileNoSplice `state:"nosave"`
fsutil.FileNotDirReaddir `state:"nosave"`
fsutil.FileNoopRelease `state:"nosave"`
fsutil.FileNoopFlush `state:"nosave"`
fsutil.FileNoopFsync `state:"nosave"`
fsutil.FileNoopWrite `state:"nosave"`
fsutil.FileUseInodeUnstableAttr `state:"nosave"`
waiter.AlwaysReady `state:"nosave"`
// arg is the type of exec argument this file contains.
arg execArgType
// t is the Task to read the exec arg line from.
t *kernel.Task
}
var _ fs.FileOperations = (*execArgFile)(nil)
// Read reads the exec arg from the process's address space..
func (f *execArgFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
if offset < 0 {
return 0, linuxerr.EINVAL
}
m, err := getTaskMM(f.t)
if err != nil {
return 0, err
}
defer m.DecUsers(ctx)
// Figure out the bounds of the exec arg we are trying to read.
var execArgStart, execArgEnd hostarch.Addr
switch f.arg {
case cmdlineExecArg:
execArgStart, execArgEnd = m.ArgvStart(), m.ArgvEnd()
case environExecArg:
execArgStart, execArgEnd = m.EnvvStart(), m.EnvvEnd()
default:
panic(fmt.Sprintf("unknown exec arg type %v", f.arg))
}
if execArgStart == 0 || execArgEnd == 0 {
// Don't attempt to read before the start/end are set up.
return 0, io.EOF
}
start, ok := execArgStart.AddLength(uint64(offset))
if !ok {
return 0, io.EOF
}
if start >= execArgEnd {
return 0, io.EOF
}
length := int(execArgEnd - start)
if dstlen := dst.NumBytes(); int64(length) > dstlen {
length = int(dstlen)
}
buf := make([]byte, length)
// N.B. Technically this should be usermem.IOOpts.IgnorePermissions = true
// until Linux 4.9 (272ddc8b3735 "proc: don't use FOLL_FORCE for reading
// cmdline and environment").
copyN, err := m.CopyIn(ctx, start, buf, usermem.IOOpts{})
if copyN == 0 {
// Nothing to copy.
return 0, err
}
buf = buf[:copyN]
// On Linux, if the NUL byte at the end of the argument vector has been
// overwritten, it continues reading the environment vector as part of
// the argument vector.
if f.arg == cmdlineExecArg && buf[copyN-1] != 0 {
// Linux will limit the return up to and including the first null character in argv
copyN = bytes.IndexByte(buf, 0)
if copyN == -1 {
copyN = len(buf)
}
// If we found a NUL character in argv, return upto and including that character.
if copyN < len(buf) {
buf = buf[:copyN]
} else { // Otherwise return into envp.
lengthEnvv := int(m.EnvvEnd() - m.EnvvStart())
// Upstream limits the returned amount to one page of slop.
// https://elixir.bootlin.com/linux/v4.20/source/fs/proc/base.c#L208
// we'll return one page total between argv and envp because of the
// above page restrictions.
if lengthEnvv > hostarch.PageSize-len(buf) {
lengthEnvv = hostarch.PageSize - len(buf)
}
// Make a new buffer to fit the whole thing
tmp := make([]byte, length+lengthEnvv)
copyNE, err := m.CopyIn(ctx, m.EnvvStart(), tmp[copyN:], usermem.IOOpts{})
if err != nil {
return 0, err
}
// Linux will return envp up to and including the first NUL character, so find it.
for i, c := range tmp[copyN:] {
if c == 0 {
copyNE = i
break
}
}
copy(tmp, buf)
buf = tmp[:copyN+copyNE]
}
}
n, dstErr := dst.CopyOut(ctx, buf)
if dstErr != nil {
return int64(n), dstErr
}
return int64(n), err
}
// LINT.ThenChange(../../fsimpl/proc/task.go)
|
