From db376e13924be59182ed4df95762328febf26298 Mon Sep 17 00:00:00 2001 From: Fabricio Voznika Date: Wed, 8 Jan 2020 10:30:50 -0800 Subject: Make /proc/[pid] offset start at TGID_OFFSET Updates #1195 PiperOrigin-RevId: 288725745 --- pkg/sentry/fsimpl/proc/tasks.go | 102 ++++++++++++++++++------ pkg/sentry/fsimpl/proc/tasks_test.go | 147 ++++++++++++++++++++++++++++++++++- 2 files changed, 223 insertions(+), 26 deletions(-) diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go index 50b2a832f..d8f92d52f 100644 --- a/pkg/sentry/fsimpl/proc/tasks.go +++ b/pkg/sentry/fsimpl/proc/tasks.go @@ -27,7 +27,11 @@ import ( "gvisor.dev/gvisor/pkg/syserror" ) -const defaultPermission = 0444 +const ( + defaultPermission = 0444 + selfName = "self" + threadSelfName = "thread-self" +) // InoGenerator generates unique inode numbers for a given filesystem. type InoGenerator interface { @@ -45,6 +49,11 @@ type tasksInode struct { inoGen InoGenerator pidns *kernel.PIDNamespace + + // '/proc/self' and '/proc/thread-self' have custom directory offsets in + // Linux. So handle them outside of OrderedChildren. + selfSymlink *vfs.Dentry + threadSelfSymlink *vfs.Dentry } var _ kernfs.Inode = (*tasksInode)(nil) @@ -54,20 +63,20 @@ func newTasksInode(inoGen InoGenerator, k *kernel.Kernel, pidns *kernel.PIDNames contents := map[string]*kernfs.Dentry{ //"cpuinfo": newCPUInfo(ctx, msrc), //"filesystems": seqfile.NewSeqFileInode(ctx, &filesystemsData{}, msrc), - "loadavg": newDentry(root, inoGen.NextIno(), defaultPermission, &loadavgData{}), - "meminfo": newDentry(root, inoGen.NextIno(), defaultPermission, &meminfoData{k: k}), - "mounts": kernfs.NewStaticSymlink(root, inoGen.NextIno(), defaultPermission, "self/mounts"), - "self": newSelfSymlink(root, inoGen.NextIno(), defaultPermission, pidns), - "stat": newDentry(root, inoGen.NextIno(), defaultPermission, &statData{k: k}), - "thread-self": newThreadSelfSymlink(root, inoGen.NextIno(), defaultPermission, pidns), + "loadavg": newDentry(root, inoGen.NextIno(), defaultPermission, &loadavgData{}), + "meminfo": newDentry(root, inoGen.NextIno(), defaultPermission, &meminfoData{k: k}), + "mounts": kernfs.NewStaticSymlink(root, inoGen.NextIno(), defaultPermission, "self/mounts"), + "stat": newDentry(root, inoGen.NextIno(), defaultPermission, &statData{k: k}), //"uptime": newUptime(ctx, msrc), //"version": newVersionData(root, inoGen.NextIno(), k), "version": newDentry(root, inoGen.NextIno(), defaultPermission, &versionData{k: k}), } inode := &tasksInode{ - pidns: pidns, - inoGen: inoGen, + pidns: pidns, + inoGen: inoGen, + selfSymlink: newSelfSymlink(root, inoGen.NextIno(), 0444, pidns).VFSDentry(), + threadSelfSymlink: newThreadSelfSymlink(root, inoGen.NextIno(), 0444, pidns).VFSDentry(), } inode.InodeAttrs.Init(root, inoGen.NextIno(), linux.ModeDirectory|0555) @@ -86,6 +95,13 @@ func (i *tasksInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, erro // Try to lookup a corresponding task. tid, err := strconv.ParseUint(name, 10, 64) if err != nil { + // If it failed to parse, check if it's one of the special handled files. + switch name { + case selfName: + return i.selfSymlink, nil + case threadSelfName: + return i.threadSelfSymlink, nil + } return nil, syserror.ENOENT } @@ -104,41 +120,81 @@ func (i *tasksInode) Valid(ctx context.Context) bool { } // IterDirents implements kernfs.inodeDynamicLookup. -// -// TODO(gvisor.dev/issue/1195): Use tgid N offset = TGID_OFFSET + N. -func (i *tasksInode) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, offset, relOffset int64) (int64, error) { - var tids []int +func (i *tasksInode) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, offset, _ int64) (int64, error) { + // fs/proc/internal.h: #define FIRST_PROCESS_ENTRY 256 + const FIRST_PROCESS_ENTRY = 256 + + // Use maxTaskID to shortcut searches that will result in 0 entries. + const maxTaskID = kernel.TasksLimit + 1 + if offset >= maxTaskID { + return offset, nil + } + + // According to Linux (fs/proc/base.c:proc_pid_readdir()), process directories + // start at offset FIRST_PROCESS_ENTRY with '/proc/self', followed by + // '/proc/thread-self' and then '/proc/[pid]'. + if offset < FIRST_PROCESS_ENTRY { + offset = FIRST_PROCESS_ENTRY + } + + if offset == FIRST_PROCESS_ENTRY { + dirent := vfs.Dirent{ + Name: selfName, + Type: linux.DT_LNK, + Ino: i.inoGen.NextIno(), + NextOff: offset + 1, + } + if !cb.Handle(dirent) { + return offset, nil + } + offset++ + } + if offset == FIRST_PROCESS_ENTRY+1 { + dirent := vfs.Dirent{ + Name: threadSelfName, + Type: linux.DT_LNK, + Ino: i.inoGen.NextIno(), + NextOff: offset + 1, + } + if !cb.Handle(dirent) { + return offset, nil + } + offset++ + } - // Collect all tasks. Per linux we only include it in directory listings if - // it's the leader. But for whatever crazy reason, you can still walk to the - // given node. + // Collect all tasks that TGIDs are greater than the offset specified. Per + // Linux we only include in directory listings if it's the leader. But for + // whatever crazy reason, you can still walk to the given node. + var tids []int + startTid := offset - FIRST_PROCESS_ENTRY - 2 for _, tg := range i.pidns.ThreadGroups() { + tid := i.pidns.IDOfThreadGroup(tg) + if int64(tid) < startTid { + continue + } if leader := tg.Leader(); leader != nil { - tids = append(tids, int(i.pidns.IDOfThreadGroup(tg))) + tids = append(tids, int(tid)) } } if len(tids) == 0 { return offset, nil } - if relOffset >= int64(len(tids)) { - return offset, nil - } sort.Ints(tids) - for _, tid := range tids[relOffset:] { + for _, tid := range tids { dirent := vfs.Dirent{ Name: strconv.FormatUint(uint64(tid), 10), Type: linux.DT_DIR, Ino: i.inoGen.NextIno(), - NextOff: offset + 1, + NextOff: FIRST_PROCESS_ENTRY + 2 + int64(tid) + 1, } if !cb.Handle(dirent) { return offset, nil } offset++ } - return offset, nil + return maxTaskID, nil } // Open implements kernfs.Inode. diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go index 2560fcef9..ca8c87ec2 100644 --- a/pkg/sentry/fsimpl/proc/tasks_test.go +++ b/pkg/sentry/fsimpl/proc/tasks_test.go @@ -16,6 +16,7 @@ package proc import ( "fmt" + "math" "path" "strconv" "testing" @@ -30,6 +31,18 @@ import ( "gvisor.dev/gvisor/pkg/syserror" ) +var ( + // Next offset 256 by convention. Adds 1 for the next offset. + selfLink = vfs.Dirent{Type: linux.DT_LNK, NextOff: 256 + 0 + 1} + threadSelfLink = vfs.Dirent{Type: linux.DT_LNK, NextOff: 256 + 1 + 1} + + // /proc/[pid] next offset starts at 256+2 (files above), then adds the + // PID, and adds 1 for the next offset. + proc1 = vfs.Dirent{Type: linux.DT_DIR, NextOff: 258 + 1 + 1} + proc2 = vfs.Dirent{Type: linux.DT_DIR, NextOff: 258 + 2 + 1} + proc3 = vfs.Dirent{Type: linux.DT_DIR, NextOff: 258 + 3 + 1} +) + type testIterDirentsCallback struct { dirents []vfs.Dirent } @@ -59,9 +72,9 @@ func checkTasksStaticFiles(gots []vfs.Dirent) ([]vfs.Dirent, error) { "loadavg": {Type: linux.DT_REG}, "meminfo": {Type: linux.DT_REG}, "mounts": {Type: linux.DT_LNK}, - "self": {Type: linux.DT_LNK}, + "self": selfLink, "stat": {Type: linux.DT_REG}, - "thread-self": {Type: linux.DT_LNK}, + "thread-self": threadSelfLink, "version": {Type: linux.DT_REG}, } return checkFiles(gots, wants) @@ -93,6 +106,9 @@ func checkFiles(gots []vfs.Dirent, wants map[string]vfs.Dirent) ([]vfs.Dirent, e if want.Type != got.Type { return gots, fmt.Errorf("wrong file type, want: %v, got: %v: %+v", want.Type, got.Type, got) } + if want.NextOff != 0 && want.NextOff != got.NextOff { + return gots, fmt.Errorf("wrong dirent offset, want: %v, got: %v: %+v", want.NextOff, got.NextOff, got) + } delete(wants, got.Name) gots = append(gots[0:i], gots[i+1:]...) @@ -154,7 +170,7 @@ func TestTasksEmpty(t *testing.T) { t.Error(err.Error()) } if len(cb.dirents) != 0 { - t.Error("found more files than expected: %+v", cb.dirents) + t.Errorf("found more files than expected: %+v", cb.dirents) } } @@ -216,6 +232,11 @@ func TestTasks(t *testing.T) { if !found { t.Errorf("Additional task ID %d listed: %v", pid, tasks) } + // Next offset starts at 256+2 ('self' and 'thread-self'), then adds the + // PID, and adds 1 for the next offset. + if want := int64(256 + 2 + pid + 1); d.NextOff != want { + t.Errorf("Wrong dirent offset want: %d got: %d: %+v", want, d.NextOff, d) + } } // Test lookup. @@ -246,6 +267,126 @@ func TestTasks(t *testing.T) { } } +func TestTasksOffset(t *testing.T) { + ctx, vfsObj, root, err := setup() + if err != nil { + t.Fatalf("Setup failed: %v", err) + } + defer root.DecRef() + + k := kernel.KernelFromContext(ctx) + for i := 0; i < 3; i++ { + tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits()) + if _, err := createTask(ctx, fmt.Sprintf("name-%d", i), tc); err != nil { + t.Fatalf("CreateTask(): %v", err) + } + } + + for _, tc := range []struct { + name string + offset int64 + wants map[string]vfs.Dirent + }{ + { + name: "small offset", + offset: 100, + wants: map[string]vfs.Dirent{ + "self": selfLink, + "thread-self": threadSelfLink, + "1": proc1, + "2": proc2, + "3": proc3, + }, + }, + { + name: "offset at start", + offset: 256, + wants: map[string]vfs.Dirent{ + "self": selfLink, + "thread-self": threadSelfLink, + "1": proc1, + "2": proc2, + "3": proc3, + }, + }, + { + name: "skip /proc/self", + offset: 257, + wants: map[string]vfs.Dirent{ + "thread-self": threadSelfLink, + "1": proc1, + "2": proc2, + "3": proc3, + }, + }, + { + name: "skip symlinks", + offset: 258, + wants: map[string]vfs.Dirent{ + "1": proc1, + "2": proc2, + "3": proc3, + }, + }, + { + name: "skip first process", + offset: 260, + wants: map[string]vfs.Dirent{ + "2": proc2, + "3": proc3, + }, + }, + { + name: "last process", + offset: 261, + wants: map[string]vfs.Dirent{ + "3": proc3, + }, + }, + { + name: "after last", + offset: 262, + wants: nil, + }, + { + name: "TaskLimit+1", + offset: kernel.TasksLimit + 1, + wants: nil, + }, + { + name: "max", + offset: math.MaxInt64, + wants: nil, + }, + } { + t.Run(tc.name, func(t *testing.T) { + fd, err := vfsObj.OpenAt( + ctx, + auth.CredentialsFromContext(ctx), + &vfs.PathOperation{Root: root, Start: root, Path: fspath.Parse("/")}, + &vfs.OpenOptions{}, + ) + if err != nil { + t.Fatalf("vfsfs.OpenAt(/) failed: %v", err) + } + if _, err := fd.Impl().Seek(ctx, tc.offset, linux.SEEK_SET); err != nil { + t.Fatalf("Seek(%d, SEEK_SET): %v", tc.offset, err) + } + + cb := testIterDirentsCallback{} + if err := fd.Impl().IterDirents(ctx, &cb); err != nil { + t.Fatalf("IterDirents(): %v", err) + } + if cb.dirents, err = checkFiles(cb.dirents, tc.wants); err != nil { + t.Error(err.Error()) + } + if len(cb.dirents) != 0 { + t.Errorf("found more files than expected: %+v", cb.dirents) + } + }) + } +} + func TestTask(t *testing.T) { ctx, vfsObj, root, err := setup() if err != nil { -- cgit v1.2.3