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// 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.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
"gvisor.googlesource.com/gvisor/pkg/waiter"
)
// idMapInodeOperations implements fs.InodeOperations for
// /proc/[pid]/{uid,gid}_map.
//
// +stateify savable
type idMapInodeOperations struct {
fsutil.InodeGenericChecker `state:"nosave"`
fsutil.InodeNoopRelease `state:"nosave"`
fsutil.InodeNoopWriteOut `state:"nosave"`
fsutil.InodeNotDirectory `state:"nosave"`
fsutil.InodeNotMappable `state:"nosave"`
fsutil.InodeNotSocket `state:"nosave"`
fsutil.InodeNotSymlink `state:"nosave"`
fsutil.InodeNotTruncatable `state:"nosave"`
fsutil.InodeVirtual `state:"nosave"`
fsutil.InodeSimpleAttributes
fsutil.InodeSimpleExtendedAttributes
t *kernel.Task
gids bool
}
var _ fs.InodeOperations = (*idMapInodeOperations)(nil)
// newUIDMap returns a new uid_map file.
func newUIDMap(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
return newIDMap(t, msrc, false /* gids */)
}
// newGIDMap returns a new gid_map file.
func newGIDMap(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
return newIDMap(t, msrc, true /* gids */)
}
func newIDMap(t *kernel.Task, msrc *fs.MountSource, gids bool) *fs.Inode {
return newProcInode(&idMapInodeOperations{
InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(t, fs.RootOwner, fs.FilePermsFromMode(0644), linux.PROC_SUPER_MAGIC),
t: t,
gids: gids,
}, msrc, fs.SpecialFile, t)
}
// GetFile implements fs.InodeOperations.GetFile.
func (imio *idMapInodeOperations) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
return fs.NewFile(ctx, dirent, flags, &idMapFileOperations{
iops: imio,
}), nil
}
// +stateify savable
type idMapFileOperations struct {
waiter.AlwaysReady `state:"nosave"`
fsutil.FileGenericSeek `state:"nosave"`
fsutil.FileNoIoctl `state:"nosave"`
fsutil.FileNoMMap `state:"nosave"`
fsutil.FileNoopFlush `state:"nosave"`
fsutil.FileNoopFsync `state:"nosave"`
fsutil.FileNoopRelease `state:"nosave"`
fsutil.FileNotDirReaddir `state:"nosave"`
fsutil.FileUseInodeUnstableAttr `state:"nosave"`
iops *idMapInodeOperations
}
var _ fs.FileOperations = (*idMapFileOperations)(nil)
// "There is an (arbitrary) limit on the number of lines in the file. As at
// Linux 3.18, the limit is five lines." - user_namespaces(7)
const maxIDMapLines = 5
// Read implements fs.FileOperations.Read.
func (imfo *idMapFileOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
if offset < 0 {
return 0, syserror.EINVAL
}
var entries []auth.IDMapEntry
if imfo.iops.gids {
entries = imfo.iops.t.UserNamespace().GIDMap()
} else {
entries = imfo.iops.t.UserNamespace().UIDMap()
}
var buf bytes.Buffer
for _, e := range entries {
fmt.Fprintf(&buf, "%10d %10d %10d\n", e.FirstID, e.FirstParentID, e.Length)
}
if offset >= int64(buf.Len()) {
return 0, io.EOF
}
n, err := dst.CopyOut(ctx, buf.Bytes()[offset:])
return int64(n), err
}
// Write implements fs.FileOperations.Write.
func (imfo *idMapFileOperations) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
// "In addition, the number of bytes written to the file must be less than
// the system page size, and the write must be performed at the start of
// the file ..." - user_namespaces(7)
srclen := src.NumBytes()
if srclen >= usermem.PageSize || offset != 0 {
return 0, syserror.EINVAL
}
b := make([]byte, srclen)
if _, err := src.CopyIn(ctx, b); err != nil {
return 0, err
}
// Truncate from the first NULL byte.
var nul int64
nul = int64(bytes.IndexByte(b, 0))
if nul == -1 {
nul = srclen
}
b = b[:nul]
// Remove the last \n.
if nul >= 1 && b[nul-1] == '\n' {
b = b[:nul-1]
}
lines := bytes.SplitN(b, []byte("\n"), maxIDMapLines+1)
if len(lines) > maxIDMapLines {
return 0, syserror.EINVAL
}
entries := make([]auth.IDMapEntry, len(lines))
for i, l := range lines {
var e auth.IDMapEntry
_, err := fmt.Sscan(string(l), &e.FirstID, &e.FirstParentID, &e.Length)
if err != nil {
return 0, syserror.EINVAL
}
entries[i] = e
}
var err error
if imfo.iops.gids {
err = imfo.iops.t.UserNamespace().SetGIDMap(ctx, entries)
} else {
err = imfo.iops.t.UserNamespace().SetUIDMap(ctx, entries)
}
if err != nil {
return 0, err
}
// On success, Linux's kernel/user_namespace.c:map_write() always returns
// count, even if fewer bytes were used.
return int64(srclen), nil
}
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