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// Copyright 2019 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"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/mm"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/sentry/vfs/lock"
"gvisor.dev/gvisor/pkg/syserror"
)
// taskInode represents the inode for /proc/PID/ directory.
//
// +stateify savable
type taskInode struct {
kernfs.InodeNotSymlink
kernfs.InodeDirectoryNoNewChildren
kernfs.InodeNoDynamicLookup
kernfs.InodeAttrs
kernfs.OrderedChildren
locks lock.FileLocks
task *kernel.Task
}
var _ kernfs.Inode = (*taskInode)(nil)
func (fs *filesystem) newTaskInode(task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool, cgroupControllers map[string]string) *kernfs.Dentry {
// TODO(gvisor.dev/issue/164): Fail with ESRCH if task exited.
contents := map[string]*kernfs.Dentry{
"auxv": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &auxvData{task: task}),
"cmdline": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &cmdlineData{task: task, arg: cmdlineDataArg}),
"comm": fs.newComm(task, fs.NextIno(), 0444),
"environ": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &cmdlineData{task: task, arg: environDataArg}),
"exe": fs.newExeSymlink(task, fs.NextIno()),
"fd": fs.newFDDirInode(task),
"fdinfo": fs.newFDInfoDirInode(task),
"gid_map": fs.newTaskOwnedFile(task, fs.NextIno(), 0644, &idMapData{task: task, gids: true}),
"io": fs.newTaskOwnedFile(task, fs.NextIno(), 0400, newIO(task, isThreadGroup)),
"maps": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &mapsData{task: task}),
"mountinfo": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &mountInfoData{task: task}),
"mounts": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &mountsData{task: task}),
"net": fs.newTaskNetDir(task),
"ns": fs.newTaskOwnedDir(task, fs.NextIno(), 0511, map[string]*kernfs.Dentry{
"net": fs.newNamespaceSymlink(task, fs.NextIno(), "net"),
"pid": fs.newNamespaceSymlink(task, fs.NextIno(), "pid"),
"user": fs.newNamespaceSymlink(task, fs.NextIno(), "user"),
}),
"oom_score": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, newStaticFile("0\n")),
"oom_score_adj": fs.newTaskOwnedFile(task, fs.NextIno(), 0644, &oomScoreAdj{task: task}),
"smaps": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &smapsData{task: task}),
"stat": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &taskStatData{task: task, pidns: pidns, tgstats: isThreadGroup}),
"statm": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &statmData{task: task}),
"status": fs.newTaskOwnedFile(task, fs.NextIno(), 0444, &statusData{task: task, pidns: pidns}),
"uid_map": fs.newTaskOwnedFile(task, fs.NextIno(), 0644, &idMapData{task: task, gids: false}),
}
if isThreadGroup {
contents["task"] = fs.newSubtasks(task, pidns, cgroupControllers)
}
if len(cgroupControllers) > 0 {
contents["cgroup"] = fs.newTaskOwnedFile(task, fs.NextIno(), 0444, newCgroupData(cgroupControllers))
}
taskInode := &taskInode{task: task}
// Note: credentials are overridden by taskOwnedInode.
taskInode.InodeAttrs.Init(task.Credentials(), linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), linux.ModeDirectory|0555)
inode := &taskOwnedInode{Inode: taskInode, owner: task}
dentry := &kernfs.Dentry{}
dentry.Init(inode)
taskInode.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
links := taskInode.OrderedChildren.Populate(dentry, contents)
taskInode.IncLinks(links)
return dentry
}
// Valid implements kernfs.inodeDynamicLookup. This inode remains valid as long
// as the task is still running. When it's dead, another tasks with the same
// PID could replace it.
func (i *taskInode) Valid(ctx context.Context) bool {
return i.task.ExitState() != kernel.TaskExitDead
}
// Open implements kernfs.Inode.
func (i *taskInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
if err != nil {
return nil, err
}
return fd.VFSFileDescription(), nil
}
// SetStat implements Inode.SetStat not allowing inode attributes to be changed.
func (*taskInode) SetStat(context.Context, *vfs.Filesystem, *auth.Credentials, vfs.SetStatOptions) error {
return syserror.EPERM
}
// taskOwnedInode implements kernfs.Inode and overrides inode owner with task
// effective user and group.
type taskOwnedInode struct {
kernfs.Inode
// owner is the task that owns this inode.
owner *kernel.Task
}
var _ kernfs.Inode = (*taskOwnedInode)(nil)
func (fs *filesystem) newTaskOwnedFile(task *kernel.Task, ino uint64, perm linux.FileMode, inode dynamicInode) *kernfs.Dentry {
// Note: credentials are overridden by taskOwnedInode.
inode.Init(task.Credentials(), linux.UNNAMED_MAJOR, fs.devMinor, ino, inode, perm)
taskInode := &taskOwnedInode{Inode: inode, owner: task}
d := &kernfs.Dentry{}
d.Init(taskInode)
return d
}
func (fs *filesystem) newTaskOwnedDir(task *kernel.Task, ino uint64, perm linux.FileMode, children map[string]*kernfs.Dentry) *kernfs.Dentry {
dir := &kernfs.StaticDirectory{}
// Note: credentials are overridden by taskOwnedInode.
dir.Init(task.Credentials(), linux.UNNAMED_MAJOR, fs.devMinor, ino, perm)
inode := &taskOwnedInode{Inode: dir, owner: task}
d := &kernfs.Dentry{}
d.Init(inode)
dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
links := dir.OrderedChildren.Populate(d, children)
dir.IncLinks(links)
return d
}
// Stat implements kernfs.Inode.
func (i *taskOwnedInode) Stat(fs *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, error) {
stat, err := i.Inode.Stat(fs, opts)
if err != nil {
return linux.Statx{}, err
}
if opts.Mask&(linux.STATX_UID|linux.STATX_GID) != 0 {
uid, gid := i.getOwner(linux.FileMode(stat.Mode))
if opts.Mask&linux.STATX_UID != 0 {
stat.UID = uint32(uid)
}
if opts.Mask&linux.STATX_GID != 0 {
stat.GID = uint32(gid)
}
}
return stat, nil
}
// CheckPermissions implements kernfs.Inode.
func (i *taskOwnedInode) CheckPermissions(_ context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
mode := i.Mode()
uid, gid := i.getOwner(mode)
return vfs.GenericCheckPermissions(creds, ats, mode, uid, gid)
}
func (i *taskOwnedInode) getOwner(mode linux.FileMode) (auth.KUID, auth.KGID) {
// By default, set the task owner as the file owner.
creds := i.owner.Credentials()
uid := creds.EffectiveKUID
gid := creds.EffectiveKGID
// Linux doesn't apply dumpability adjustments to world readable/executable
// directories so that applications can stat /proc/PID to determine the
// effective UID of a process. See fs/proc/base.c:task_dump_owner.
if mode.FileType() == linux.ModeDirectory && mode.Permissions() == 0555 {
return uid, gid
}
// If the task is not dumpable, then root (in the namespace preferred)
// owns the file.
m := getMM(i.owner)
if m == nil {
return auth.RootKUID, auth.RootKGID
}
if m.Dumpability() != mm.UserDumpable {
uid = auth.RootKUID
if kuid := creds.UserNamespace.MapToKUID(auth.RootUID); kuid.Ok() {
uid = kuid
}
gid = auth.RootKGID
if kgid := creds.UserNamespace.MapToKGID(auth.RootGID); kgid.Ok() {
gid = kgid
}
}
return uid, gid
}
func newIO(t *kernel.Task, isThreadGroup bool) *ioData {
if isThreadGroup {
return &ioData{ioUsage: t.ThreadGroup()}
}
return &ioData{ioUsage: t}
}
// newCgroupData creates inode that shows cgroup information.
// From man 7 cgroups: "For each cgroup hierarchy of which the process is a
// member, there is one entry containing three colon-separated fields:
// hierarchy-ID:controller-list:cgroup-path"
func newCgroupData(controllers map[string]string) dynamicInode {
var buf bytes.Buffer
// The hierarchy ids must be positive integers (for cgroup v1), but the
// exact number does not matter, so long as they are unique. We can
// just use a counter, but since linux sorts this file in descending
// order, we must count down to preserve this behavior.
i := len(controllers)
for name, dir := range controllers {
fmt.Fprintf(&buf, "%d:%s:%s\n", i, name, dir)
i--
}
return newStaticFile(buf.String())
}
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