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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"
"sort"
"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"
)
// forEachMountSource runs f for the process root mount and each mount that is a
// descendant of the root.
func forEachMountSource(t *kernel.Task, fn func(string, *fs.MountSource)) {
var fsctx *kernel.FSContext
t.WithMuLocked(func(t *kernel.Task) {
fsctx = t.FSContext()
})
if fsctx == nil {
// The task has been destroyed. Nothing to show here.
return
}
// All mount points must be relative to the rootDir, and mounts outside
// will be excluded.
rootDir := fsctx.RootDirectory()
if rootDir == nil {
// The task has been destroyed. Nothing to show here.
return
}
defer rootDir.DecRef()
if rootDir.Inode == nil {
panic(fmt.Sprintf("root dirent has nil inode: %+v", rootDir))
}
if rootDir.Inode.MountSource == nil {
panic(fmt.Sprintf("root dirent has nil mount: %+v", rootDir))
}
ms := append(rootDir.Inode.MountSource.Submounts(), rootDir.Inode.MountSource)
sort.Slice(ms, func(i, j int) bool {
return ms[i].ID() < ms[j].ID()
})
for _, m := range ms {
mroot := m.Root()
mountPath, desc := mroot.FullName(rootDir)
mroot.DecRef()
if !desc {
// MountSources that are not descendants of the chroot jail are ignored.
continue
}
fn(mountPath, m)
}
}
// mountInfoFile is used to implement /proc/[pid]/mountinfo.
//
// +stateify savable
type mountInfoFile struct {
t *kernel.Task
}
// NeedsUpdate implements SeqSource.NeedsUpdate.
func (mif *mountInfoFile) NeedsUpdate(_ int64) bool {
return true
}
// ReadSeqFileData implements SeqSource.ReadSeqFileData.
func (mif *mountInfoFile) ReadSeqFileData(ctx context.Context, handle seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
if handle != nil {
return nil, 0
}
var buf bytes.Buffer
forEachMountSource(mif.t, func(mountPath string, m *fs.MountSource) {
// Format:
// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
// (1) MountSource ID.
fmt.Fprintf(&buf, "%d ", m.ID())
// (2) Parent ID (or this ID if there is no parent).
pID := m.ID()
if p := m.Parent(); p != nil {
pID = p.ID()
}
fmt.Fprintf(&buf, "%d ", pID)
// (3) Major:Minor device ID. We don't have a superblock, so we
// just use the root inode device number.
mroot := m.Root()
sa := mroot.Inode.StableAttr
mroot.DecRef()
fmt.Fprintf(&buf, "%d:%d ", sa.DeviceFileMajor, sa.DeviceFileMinor)
// (4) Root: the pathname of the directory in the filesystem
// which forms the root of this mount.
//
// NOTE(b/78135857): This will always be "/" until we implement
// bind mounts.
fmt.Fprintf(&buf, "/ ")
// (5) Mount point (relative to process root).
fmt.Fprintf(&buf, "%s ", mountPath)
// (6) Mount options.
opts := "rw"
if m.Flags.ReadOnly {
opts = "ro"
}
if m.Flags.NoAtime {
opts += ",noatime"
}
if m.Flags.NoExec {
opts += ",noexec"
}
fmt.Fprintf(&buf, "%s ", opts)
// (7) Optional fields: zero or more fields of the form "tag[:value]".
// (8) Separator: the end of the optional fields is marked by a single hyphen.
fmt.Fprintf(&buf, "- ")
// (9) Filesystem type.
name := "none"
if m.Filesystem != nil {
name = m.Filesystem.Name()
}
fmt.Fprintf(&buf, "%s ", name)
// (10) Mount source: filesystem-specific information or "none".
fmt.Fprintf(&buf, "none ")
// (11) Superblock options. Only "ro/rw" is supported for now,
// and is the same as the filesystem option.
fmt.Fprintf(&buf, "%s\n", opts)
})
return []seqfile.SeqData{{Buf: buf.Bytes(), Handle: (*mountInfoFile)(nil)}}, 0
}
// mountsFile is used to implement /proc/[pid]/mounts.
//
// +stateify savable
type mountsFile struct {
t *kernel.Task
}
// NeedsUpdate implements SeqSource.NeedsUpdate.
func (mf *mountsFile) NeedsUpdate(_ int64) bool {
return true
}
// ReadSeqFileData implements SeqSource.ReadSeqFileData.
func (mf *mountsFile) ReadSeqFileData(ctx context.Context, handle seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
if handle != nil {
return nil, 0
}
var buf bytes.Buffer
forEachMountSource(mf.t, func(mountPath string, m *fs.MountSource) {
// Format:
// <special device or remote filesystem> <mount point> <filesystem type> <mount options> <needs dump> <fsck order>
//
// We use the filesystem name as the first field, since there
// is no real block device we can point to, and we also should
// not expose anything about the remote filesystem.
//
// Only ro/rw option is supported for now.
//
// The "needs dump"and fsck flags are always 0, which is allowed.
opts := "rw"
if m.Flags.ReadOnly {
opts = "ro"
}
name := "none"
if m.Filesystem != nil {
name = m.Filesystem.Name()
}
fmt.Fprintf(&buf, "%s %s %s %s %d %d\n", "none", mountPath, name, opts, 0, 0)
})
return []seqfile.SeqData{{Buf: buf.Bytes(), Handle: (*mountsFile)(nil)}}, 0
}
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