1 files changed, 234 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
new file mode 100755
index 000000000..888afc0fd
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -0,0 +1,234 @@
+// 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/syserror"
+)
+
+// taskInode represents the inode for /proc/PID/ directory.
+//
+// +stateify savable
+type taskInode struct {
+	kernfs.InodeNotSymlink
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNoDynamicLookup
+	kernfs.InodeAttrs
+	kernfs.OrderedChildren
+
+	task *kernel.Task
+}
+
+var _ kernfs.Inode = (*taskInode)(nil)
+
+func newTaskInode(inoGen InoGenerator, task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool, cgroupControllers map[string]string) *kernfs.Dentry {
+	contents := map[string]*kernfs.Dentry{
+		"auxv":      newTaskOwnedFile(task, inoGen.NextIno(), 0444, &auxvData{task: task}),
+		"cmdline":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &cmdlineData{task: task, arg: cmdlineDataArg}),
+		"comm":      newComm(task, inoGen.NextIno(), 0444),
+		"environ":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &cmdlineData{task: task, arg: environDataArg}),
+		"exe":       newExeSymlink(task, inoGen.NextIno()),
+		"fd":        newFDDirInode(task, inoGen),
+		"fdinfo":    newFDInfoDirInode(task, inoGen),
+		"gid_map":   newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: true}),
+		"io":        newTaskOwnedFile(task, inoGen.NextIno(), 0400, newIO(task, isThreadGroup)),
+		"maps":      newTaskOwnedFile(task, inoGen.NextIno(), 0444, &mapsData{task: task}),
+		"mountinfo": newTaskOwnedFile(task, inoGen.NextIno(), 0444, &mountInfoData{task: task}),
+		"mounts":    newTaskOwnedFile(task, inoGen.NextIno(), 0444, &mountsData{task: task}),
+		"net":       newTaskNetDir(task, inoGen),
+		"ns": newTaskOwnedDir(task, inoGen.NextIno(), 0511, map[string]*kernfs.Dentry{
+			"net":  newNamespaceSymlink(task, inoGen.NextIno(), "net"),
+			"pid":  newNamespaceSymlink(task, inoGen.NextIno(), "pid"),
+			"user": newNamespaceSymlink(task, inoGen.NextIno(), "user"),
+		}),
+		"oom_score":     newTaskOwnedFile(task, inoGen.NextIno(), 0444, newStaticFile("0\n")),
+		"oom_score_adj": newTaskOwnedFile(task, inoGen.NextIno(), 0644, &oomScoreAdj{task: task}),
+		"smaps":         newTaskOwnedFile(task, inoGen.NextIno(), 0444, &smapsData{task: task}),
+		"stat":          newTaskOwnedFile(task, inoGen.NextIno(), 0444, &taskStatData{task: task, pidns: pidns, tgstats: isThreadGroup}),
+		"statm":         newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statmData{task: task}),
+		"status":        newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statusData{task: task, pidns: pidns}),
+		"uid_map":       newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: false}),
+	}
+	if isThreadGroup {
+		contents["task"] = newSubtasks(task, pidns, inoGen, cgroupControllers)
+	}
+	if len(cgroupControllers) > 0 {
+		contents["cgroup"] = newTaskOwnedFile(task, inoGen.NextIno(), 0444, newCgroupData(cgroupControllers))
+	}
+
+	taskInode := &taskInode{task: task}
+	// Note: credentials are overridden by taskOwnedInode.
+	taskInode.InodeAttrs.Init(task.Credentials(), inoGen.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(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd := &kernfs.GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &i.OrderedChildren, &opts)
+	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 newTaskOwnedFile(task *kernel.Task, ino uint64, perm linux.FileMode, inode dynamicInode) *kernfs.Dentry {
+	// Note: credentials are overridden by taskOwnedInode.
+	inode.Init(task.Credentials(), ino, inode, perm)
+
+	taskInode := &taskOwnedInode{Inode: inode, owner: task}
+	d := &kernfs.Dentry{}
+	d.Init(taskInode)
+	return d
+}
+
+func 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(), 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())
+}