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// Copyright 2018 Google LLC
//
// 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"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/seqfile"
"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"
)
// An idMapSeqSource is a seqfile.SeqSource that returns UID or GID mappings
// from a task's user namespace.
//
// +stateify savable
type idMapSeqSource struct {
t *kernel.Task
gids bool
}
// NeedsUpdate implements seqfile.SeqSource.NeedsUpdate.
func (imss *idMapSeqSource) NeedsUpdate(generation int64) bool {
return true
}
// ReadSeqFileData implements seqfile.SeqSource.ReadSeqFileData.
func (imss *idMapSeqSource) ReadSeqFileData(ctx context.Context, handle seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
var start int
if handle != nil {
start = handle.(*idMapSeqHandle).value
}
var entries []auth.IDMapEntry
if imss.gids {
entries = imss.t.UserNamespace().GIDMap()
} else {
entries = imss.t.UserNamespace().UIDMap()
}
var data []seqfile.SeqData
i := 1
for _, e := range entries {
if i > start {
data = append(data, seqfile.SeqData{
Buf: idMapLineFromEntry(e),
Handle: &idMapSeqHandle{i},
})
}
i++
}
return data, 0
}
// TODO: Fix issue requiring idMapSeqHandle wrapping an int.
//
// +stateify savable
type idMapSeqHandle struct {
value int
}
// +stateify savable
type idMapSeqFile struct {
seqfile.SeqFile
}
// 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 {
imsf := &idMapSeqFile{seqfile.SeqFile{SeqSource: &idMapSeqSource{
t: t,
gids: gids,
}}}
imsf.InitEntry(t, fs.RootOwner, fs.FilePermsFromMode(0644))
return newFile(imsf, msrc, fs.SpecialFile, t)
}
func (imsf *idMapSeqFile) source() *idMapSeqSource {
return imsf.SeqFile.SeqSource.(*idMapSeqSource)
}
// "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
// DeprecatedPwritev implements fs.InodeOperations.DeprecatedPwritev.
func (imsf *idMapSeqFile) DeprecatedPwritev(ctx context.Context, 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
}
lines := bytes.SplitN(bytes.TrimSpace(b), []byte("\n"), maxIDMapLines+1)
if len(lines) > maxIDMapLines {
return 0, syserror.EINVAL
}
entries := make([]auth.IDMapEntry, len(lines))
for i, l := range lines {
e, err := idMapEntryFromLine(string(l))
if err != nil {
return 0, syserror.EINVAL
}
entries[i] = e
}
t := imsf.source().t
var err error
if imsf.source().gids {
err = t.UserNamespace().SetGIDMap(ctx, entries)
} else {
err = t.UserNamespace().SetUIDMap(ctx, entries)
}
if err != nil {
return 0, err
}
return int64(len(b)), nil
}
func idMapLineFromEntry(e auth.IDMapEntry) []byte {
var b bytes.Buffer
fmt.Fprintf(&b, "%10d %10d %10d\n", e.FirstID, e.FirstParentID, e.Length)
return b.Bytes()
}
func idMapEntryFromLine(line string) (auth.IDMapEntry, error) {
var e auth.IDMapEntry
_, err := fmt.Sscan(line, &e.FirstID, &e.FirstParentID, &e.Length)
return e, err
}
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