Stub oom_score_adj and oom_score.

Adds an oom_score_adj and oom_score proc file stub. oom_score_adj accepts
writes of values -1000 to 1000 and persists the value with the task. New tasks
inherit the parent's oom_score_adj.

oom_score is a read-only stub that always returns the value '0'.

Issue #202

PiperOrigin-RevId: 299245355

11 files changed, 330 insertions, 40 deletions

diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index 8ab8d8a02..4e9b0fc00 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -72,24 +72,26 @@ var _ fs.InodeOperations = (*taskDir)(nil)
 // newTaskDir creates a new proc task entry.
 func (p *proc) newTaskDir(t *kernel.Task, msrc *fs.MountSource, isThreadGroup bool) *fs.Inode {
 	contents := map[string]*fs.Inode{
-		"auxv":      newAuxvec(t, msrc),
-		"cmdline":   newExecArgInode(t, msrc, cmdlineExecArg),
-		"comm":      newComm(t, msrc),
-		"environ":   newExecArgInode(t, msrc, environExecArg),
-		"exe":       newExe(t, msrc),
-		"fd":        newFdDir(t, msrc),
-		"fdinfo":    newFdInfoDir(t, msrc),
-		"gid_map":   newGIDMap(t, msrc),
-		"io":        newIO(t, msrc, isThreadGroup),
-		"maps":      newMaps(t, msrc),
-		"mountinfo": seqfile.NewSeqFileInode(t, &mountInfoFile{t: t}, msrc),
-		"mounts":    seqfile.NewSeqFileInode(t, &mountsFile{t: t}, msrc),
-		"ns":        newNamespaceDir(t, msrc),
-		"smaps":     newSmaps(t, msrc),
-		"stat":      newTaskStat(t, msrc, isThreadGroup, p.pidns),
-		"statm":     newStatm(t, msrc),
-		"status":    newStatus(t, msrc, p.pidns),
-		"uid_map":   newUIDMap(t, msrc),
+		"auxv":          newAuxvec(t, msrc),
+		"cmdline":       newExecArgInode(t, msrc, cmdlineExecArg),
+		"comm":          newComm(t, msrc),
+		"environ":       newExecArgInode(t, msrc, environExecArg),
+		"exe":           newExe(t, msrc),
+		"fd":            newFdDir(t, msrc),
+		"fdinfo":        newFdInfoDir(t, msrc),
+		"gid_map":       newGIDMap(t, msrc),
+		"io":            newIO(t, msrc, isThreadGroup),
+		"maps":          newMaps(t, msrc),
+		"mountinfo":     seqfile.NewSeqFileInode(t, &mountInfoFile{t: t}, msrc),
+		"mounts":        seqfile.NewSeqFileInode(t, &mountsFile{t: t}, msrc),
+		"ns":            newNamespaceDir(t, msrc),
+		"oom_score":     newOOMScore(t, msrc),
+		"oom_score_adj": newOOMScoreAdj(t, msrc),
+		"smaps":         newSmaps(t, msrc),
+		"stat":          newTaskStat(t, msrc, isThreadGroup, p.pidns),
+		"statm":         newStatm(t, msrc),
+		"status":        newStatus(t, msrc, p.pidns),
+		"uid_map":       newUIDMap(t, msrc),
 	}
 	if isThreadGroup {
 		contents["task"] = p.newSubtasks(t, msrc)
@@ -796,4 +798,92 @@ func (f *auxvecFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequenc
 	return int64(n), err
 }
 
+// newOOMScore returns a oom_score file. It is a stub that always returns 0.
+// TODO(gvisor.dev/issue/1967)
+func newOOMScore(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
+	return newStaticProcInode(t, msrc, []byte("0\n"))
+}
+
+// oomScoreAdj is a file containing the oom_score adjustment for a task.
+//
+// +stateify savable
+type oomScoreAdj struct {
+	fsutil.SimpleFileInode
+
+	t *kernel.Task
+}
+
+// +stateify savable
+type oomScoreAdjFile struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+
+	t *kernel.Task
+}
+
+// newOOMScoreAdj returns a oom_score_adj file.
+func newOOMScoreAdj(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
+	i := &oomScoreAdj{
+		SimpleFileInode: *fsutil.NewSimpleFileInode(t, fs.RootOwner, fs.FilePermsFromMode(0644), linux.PROC_SUPER_MAGIC),
+		t:               t,
+	}
+	return newProcInode(t, i, msrc, fs.SpecialFile, t)
+}
+
+// Truncate implements fs.InodeOperations.Truncate. Truncate is called when
+// O_TRUNC is specified for any kind of existing Dirent but is not called via
+// (f)truncate for proc files.
+func (*oomScoreAdj) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (o *oomScoreAdj) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	return fs.NewFile(ctx, dirent, flags, &oomScoreAdjFile{t: o.t}), nil
+}
+
+// Read implements fs.FileOperations.Read.
+func (f *oomScoreAdjFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	if offset != 0 {
+		return 0, io.EOF
+	}
+	adj, err := f.t.OOMScoreAdj()
+	if err != nil {
+		return 0, err
+	}
+	adjBytes := []byte(strconv.FormatInt(int64(adj), 10) + "\n")
+	n, err := dst.CopyOut(ctx, adjBytes)
+	return int64(n), err
+}
+
+// Write implements fs.FileOperations.Write.
+func (f *oomScoreAdjFile) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
+	if src.NumBytes() == 0 {
+		return 0, nil
+	}
+
+	// Limit input size so as not to impact performance if input size is large.
+	src = src.TakeFirst(usermem.PageSize - 1)
+
+	var v int32
+	n, err := usermem.CopyInt32StringInVec(ctx, src.IO, src.Addrs, &v, src.Opts)
+	if err != nil {
+		return 0, err
+	}
+
+	if err := f.t.SetOOMScoreAdj(v); err != nil {
+		return 0, err
+	}
+
+	return n, nil
+}
+
 // LINT.ThenChange(../../fsimpl/proc/task.go|../../fsimpl/proc/task_files.go)
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index 2d814668a..18e5cd6f6 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -62,11 +62,13 @@ func newTaskInode(inoGen InoGenerator, task *kernel.Task, pidns *kernel.PIDNames
 			"pid":  newNamespaceSymlink(task, inoGen.NextIno(), "pid"),
 			"user": newNamespaceSymlink(task, inoGen.NextIno(), "user"),
 		}),
-		"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}),
+		"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)
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index efd3b3453..5a231ac86 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -525,3 +525,46 @@ func (i *ioData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	fmt.Fprintf(buf, "cancelled_write_bytes: %d\n", io.BytesWriteCancelled)
 	return nil
 }
+
+// oomScoreAdj is a stub of the /proc/<pid>/oom_score_adj file.
+//
+// +stateify savable
+type oomScoreAdj struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+}
+
+var _ vfs.WritableDynamicBytesSource = (*oomScoreAdj)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (o *oomScoreAdj) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	adj, err := o.task.OOMScoreAdj()
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(buf, "%d\n", adj)
+	return nil
+}
+
+// Write implements vfs.WritableDynamicBytesSource.Write.
+func (o *oomScoreAdj) Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	if src.NumBytes() == 0 {
+		return 0, nil
+	}
+
+	// Limit input size so as not to impact performance if input size is large.
+	src = src.TakeFirst(usermem.PageSize - 1)
+
+	var v int32
+	n, err := usermem.CopyInt32StringInVec(ctx, src.IO, src.Addrs, &v, src.Opts)
+	if err != nil {
+		return 0, err
+	}
+
+	if err := o.task.SetOOMScoreAdj(v); err != nil {
+		return 0, err
+	}
+
+	return n, nil
+}
diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go
index c5d531fe0..0eb401619 100644
--- a/pkg/sentry/fsimpl/proc/tasks_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_test.go
@@ -63,21 +63,23 @@ var (
 		"thread-self": threadSelfLink.NextOff,
 	}
 	taskStaticFiles = map[string]testutil.DirentType{
-		"auxv":    linux.DT_REG,
-		"cgroup":  linux.DT_REG,
-		"cmdline": linux.DT_REG,
-		"comm":    linux.DT_REG,
-		"environ": linux.DT_REG,
-		"gid_map": linux.DT_REG,
-		"io":      linux.DT_REG,
-		"maps":    linux.DT_REG,
-		"ns":      linux.DT_DIR,
-		"smaps":   linux.DT_REG,
-		"stat":    linux.DT_REG,
-		"statm":   linux.DT_REG,
-		"status":  linux.DT_REG,
-		"task":    linux.DT_DIR,
-		"uid_map": linux.DT_REG,
+		"auxv":          linux.DT_REG,
+		"cgroup":        linux.DT_REG,
+		"cmdline":       linux.DT_REG,
+		"comm":          linux.DT_REG,
+		"environ":       linux.DT_REG,
+		"gid_map":       linux.DT_REG,
+		"io":            linux.DT_REG,
+		"maps":          linux.DT_REG,
+		"ns":            linux.DT_DIR,
+		"oom_score":     linux.DT_REG,
+		"oom_score_adj": linux.DT_REG,
+		"smaps":         linux.DT_REG,
+		"stat":          linux.DT_REG,
+		"statm":         linux.DT_REG,
+		"status":        linux.DT_REG,
+		"task":          linux.DT_DIR,
+		"uid_map":       linux.DT_REG,
 	}
 )
 
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index 2cee2e6ed..c0dbbe890 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -37,6 +37,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -554,6 +555,13 @@ type Task struct {
 	//
 	// startTime is protected by mu.
 	startTime ktime.Time
+
+	// oomScoreAdj is the task's OOM score adjustment. This is currently not
+	// used but is maintained for consistency.
+	// TODO(gvisor.dev/issue/1967)
+	//
+	// oomScoreAdj is protected by mu, and is owned by the task goroutine.
+	oomScoreAdj int32
 }
 
 func (t *Task) savePtraceTracer() *Task {
@@ -847,3 +855,28 @@ func (t *Task) AbstractSockets() *AbstractSocketNamespace {
 func (t *Task) ContainerID() string {
 	return t.containerID
 }
+
+// OOMScoreAdj gets the task's OOM score adjustment.
+func (t *Task) OOMScoreAdj() (int32, error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.ExitState() == TaskExitDead {
+		return 0, syserror.ESRCH
+	}
+	return t.oomScoreAdj, nil
+}
+
+// SetOOMScoreAdj sets the task's OOM score adjustment. The value should be
+// between -1000 and 1000 inclusive.
+func (t *Task) SetOOMScoreAdj(adj int32) error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.ExitState() == TaskExitDead {
+		return syserror.ESRCH
+	}
+	if adj > 1000 || adj < -1000 {
+		return syserror.EINVAL
+	}
+	t.oomScoreAdj = adj
+	return nil
+}
diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go
index 78866f280..dda502bb8 100644
--- a/pkg/sentry/kernel/task_clone.go
+++ b/pkg/sentry/kernel/task_clone.go
@@ -264,6 +264,11 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		rseqSignature = t.rseqSignature
 	}
 
+	adj, err := t.OOMScoreAdj()
+	if err != nil {
+		return 0, nil, err
+	}
+
 	cfg := &TaskConfig{
 		Kernel:                  t.k,
 		ThreadGroup:             tg,
@@ -282,6 +287,7 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		RSeqAddr:                rseqAddr,
 		RSeqSignature:           rseqSignature,
 		ContainerID:             t.ContainerID(),
+		OOMScoreAdj:             adj,
 	}
 	if opts.NewThreadGroup {
 		cfg.Parent = t
diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go
index a5035bb7f..2bbf48bb8 100644
--- a/pkg/sentry/kernel/task_start.go
+++ b/pkg/sentry/kernel/task_start.go
@@ -93,6 +93,9 @@ type TaskConfig struct {
 
 	// ContainerID is the container the new task belongs to.
 	ContainerID string
+
+	// oomScoreAdj is the task's OOM score adjustment.
+	OOMScoreAdj int32
 }
 
 // NewTask creates a new task defined by cfg.
@@ -143,6 +146,7 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) {
 		rseqSignature:      cfg.RSeqSignature,
 		futexWaiter:        futex.NewWaiter(),
 		containerID:        cfg.ContainerID,
+		oomScoreAdj:        cfg.OOMScoreAdj,
 	}
 	t.creds.Store(cfg.Credentials)
 	t.endStopCond.L = &t.tg.signalHandlers.mu
diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index a69b0ce13..9800a0cdf 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -318,10 +318,14 @@ syscall_test(
     test = "//test/syscalls/linux:proc_test",
 )
 
-syscall_test(test = "//test/syscalls/linux:proc_pid_uid_gid_map_test")
-
 syscall_test(test = "//test/syscalls/linux:proc_net_test")
 
+syscall_test(test = "//test/syscalls/linux:proc_pid_oomscore_test")
+
+syscall_test(test = "//test/syscalls/linux:proc_pid_smaps_test")
+
+syscall_test(test = "//test/syscalls/linux:proc_pid_uid_gid_map_test")
+
 syscall_test(
     size = "medium",
     test = "//test/syscalls/linux:pselect_test",
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 0fbd556de..43455f1a3 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -1632,6 +1632,19 @@ cc_binary(
 )
 
 cc_binary(
+    name = "proc_pid_oomscore_test",
+    testonly = 1,
+    srcs = ["proc_pid_oomscore.cc"],
+    linkstatic = 1,
+    deps = [
+        "//test/util:fs_util",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "@com_google_absl//absl/strings",
+    ],
+)
+
+cc_binary(
     name = "proc_pid_smaps_test",
     testonly = 1,
     srcs = ["proc_pid_smaps.cc"],
diff --git a/test/syscalls/linux/proc.cc b/test/syscalls/linux/proc.cc
index f91187e75..5a70f6c3b 100644
--- a/test/syscalls/linux/proc.cc
+++ b/test/syscalls/linux/proc.cc
@@ -1431,6 +1431,12 @@ TEST(ProcPidFile, SubprocessRunning) {
 
   EXPECT_THAT(ReadWhileRunning("uid_map", buf, sizeof(buf)),
               SyscallSucceedsWithValue(sizeof(buf)));
+
+  EXPECT_THAT(ReadWhileRunning("oom_score", buf, sizeof(buf)),
+              SyscallSucceedsWithValue(sizeof(buf)));
+
+  EXPECT_THAT(ReadWhileRunning("oom_score_adj", buf, sizeof(buf)),
+              SyscallSucceedsWithValue(sizeof(buf)));
 }
 
 // Test whether /proc/PID/ files can be read for a zombie process.
@@ -1466,6 +1472,12 @@ TEST(ProcPidFile, SubprocessZombie) {
   EXPECT_THAT(ReadWhileZombied("uid_map", buf, sizeof(buf)),
               SyscallSucceedsWithValue(sizeof(buf)));
 
+  EXPECT_THAT(ReadWhileZombied("oom_score", buf, sizeof(buf)),
+              SyscallSucceedsWithValue(sizeof(buf)));
+
+  EXPECT_THAT(ReadWhileZombied("oom_score_adj", buf, sizeof(buf)),
+              SyscallSucceedsWithValue(sizeof(buf)));
+
   // FIXME(gvisor.dev/issue/164): Inconsistent behavior between gVisor and linux
   // on proc files.
   //
@@ -1527,6 +1539,15 @@ TEST(ProcPidFile, SubprocessExited) {
 
   EXPECT_THAT(ReadWhileExited("uid_map", buf, sizeof(buf)),
               SyscallSucceedsWithValue(sizeof(buf)));
+
+  if (!IsRunningOnGvisor()) {
+    // FIXME(gvisor.dev/issue/164): Succeeds on gVisor.
+    EXPECT_THAT(ReadWhileExited("oom_score", buf, sizeof(buf)),
+                SyscallFailsWithErrno(ESRCH));
+  }
+
+  EXPECT_THAT(ReadWhileExited("oom_score_adj", buf, sizeof(buf)),
+              SyscallFailsWithErrno(ESRCH));
 }
 
 PosixError DirContainsImpl(absl::string_view path,
diff --git a/test/syscalls/linux/proc_pid_oomscore.cc b/test/syscalls/linux/proc_pid_oomscore.cc
new file mode 100644
index 000000000..707821a3f
--- /dev/null
+++ b/test/syscalls/linux/proc_pid_oomscore.cc
@@ -0,0 +1,72 @@
+// Copyright 2020 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.
+
+#include <errno.h>
+
+#include <exception>
+#include <iostream>
+#include <string>
+
+#include "test/util/fs_util.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+PosixErrorOr<int> ReadProcNumber(std::string path) {
+  ASSIGN_OR_RETURN_ERRNO(std::string contents, GetContents(path));
+  EXPECT_EQ(contents[contents.length() - 1], '\n');
+
+  int num;
+  if (!absl::SimpleAtoi(contents, &num)) {
+    return PosixError(EINVAL, "invalid value: " + contents);
+  }
+
+  return num;
+}
+
+TEST(ProcPidOomscoreTest, BasicRead) {
+  auto const oom_score =
+      ASSERT_NO_ERRNO_AND_VALUE(ReadProcNumber("/proc/self/oom_score"));
+  EXPECT_LE(oom_score, 1000);
+  EXPECT_GE(oom_score, -1000);
+}
+
+TEST(ProcPidOomscoreAdjTest, BasicRead) {
+  auto const oom_score =
+      ASSERT_NO_ERRNO_AND_VALUE(ReadProcNumber("/proc/self/oom_score_adj"));
+
+  // oom_score_adj defaults to 0.
+  EXPECT_EQ(oom_score, 0);
+}
+
+TEST(ProcPidOomscoreAdjTest, BasicWrite) {
+  constexpr int test_value = 7;
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open("/proc/self/oom_score_adj", O_WRONLY));
+  ASSERT_THAT(
+      RetryEINTR(write)(fd.get(), std::to_string(test_value).c_str(), 1),
+      SyscallSucceeds());
+
+  auto const oom_score =
+      ASSERT_NO_ERRNO_AND_VALUE(ReadProcNumber("/proc/self/oom_score_adj"));
+  EXPECT_EQ(oom_score, test_value);
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor