Add semctl(GETPID) syscall

Also added unimplemented notification for semctl(2)
commands.

PiperOrigin-RevId: 236340672
Change-Id: I0795e3bd2e6d41d7936fabb731884df426a42478

pkg/abi/linux/sem.go

@@ -27,8 +27,9 @@ const (
 
 // ipcs ctl cmds. Source: include/uapi/linux/sem.h
 const (
-	SEM_STAT = 18
-	SEM_INFO = 19
+	SEM_STAT     = 18
+	SEM_INFO     = 19
+	SEM_STAT_ANY = 20
 )
 
 const SEM_UNDO = 0x1000

pkg/sentry/kernel/semaphore/semaphore.go

@@ -92,6 +92,7 @@ type Set struct {
 type sem struct {
 	value   int16
 	waiters waiterList `state:"zerovalue"`
+	pid     int32
 }
 
 // waiter represents a caller that is waiting for the semaphore value to
@@ -283,7 +284,7 @@ func (s *Set) Change(ctx context.Context, creds *auth.Credentials, owner fs.File
 }
 
 // SetVal overrides a semaphore value, waking up waiters as needed.
-func (s *Set) SetVal(ctx context.Context, num int32, val int16, creds *auth.Credentials) error {
+func (s *Set) SetVal(ctx context.Context, num int32, val int16, creds *auth.Credentials, pid int32) error {
 	if val < 0 || val > valueMax {
 		return syserror.ERANGE
 	}
@@ -303,15 +304,17 @@ func (s *Set) SetVal(ctx context.Context, num int32, val int16, creds *auth.Cred
 
 	// TODO: Clear undo entries in all processes
 	sem.value = val
+	sem.pid = pid
 	s.changeTime = ktime.NowFromContext(ctx)
 	sem.wakeWaiters()
 	return nil
 }
 
-// SetValAll overrides all semaphores values, waking up waiters as needed.
+// SetValAll overrides all semaphores values, waking up waiters as needed. It also
+// sets semaphore's PID which was fixed in Linux 4.6.
 //
 // 'len(vals)' must be equal to 's.Size()'.
-func (s *Set) SetValAll(ctx context.Context, vals []uint16, creds *auth.Credentials) error {
+func (s *Set) SetValAll(ctx context.Context, vals []uint16, creds *auth.Credentials, pid int32) error {
 	if len(vals) != s.Size() {
 		panic(fmt.Sprintf("vals length (%d) different that Set.Size() (%d)", len(vals), s.Size()))
 	}
@@ -335,6 +338,7 @@ func (s *Set) SetValAll(ctx context.Context, vals []uint16, creds *auth.Credenti
 
 		// TODO: Clear undo entries in all processes
 		sem.value = int16(val)
+		sem.pid = pid
 		sem.wakeWaiters()
 	}
 	s.changeTime = ktime.NowFromContext(ctx)
@@ -375,12 +379,29 @@ func (s *Set) GetValAll(creds *auth.Credentials) ([]uint16, error) {
 	return vals, nil
 }
 
+// GetPID returns the PID set when performing operations in the semaphore.
+func (s *Set) GetPID(num int32, creds *auth.Credentials) (int32, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// "The calling process must have read permission on the semaphore set."
+	if !s.checkPerms(creds, fs.PermMask{Read: true}) {
+		return 0, syserror.EACCES
+	}
+
+	sem := s.findSem(num)
+	if sem == nil {
+		return 0, syserror.ERANGE
+	}
+	return sem.pid, nil
+}
+
 // ExecuteOps attempts to execute a list of operations to the set. It only
 // succeeds when all operations can be applied. No changes are made if it fails.
 //
 // On failure, it may return an error (retries are hopeless) or it may return
 // a channel that can be waited on before attempting again.
-func (s *Set) ExecuteOps(ctx context.Context, ops []linux.Sembuf, creds *auth.Credentials) (chan struct{}, int32, error) {
+func (s *Set) ExecuteOps(ctx context.Context, ops []linux.Sembuf, creds *auth.Credentials, pid int32) (chan struct{}, int32, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -404,14 +425,14 @@ func (s *Set) ExecuteOps(ctx context.Context, ops []linux.Sembuf, creds *auth.Cr
 		return nil, 0, syserror.EACCES
 	}
 
-	ch, num, err := s.executeOps(ctx, ops)
+	ch, num, err := s.executeOps(ctx, ops, pid)
 	if err != nil {
 		return nil, 0, err
 	}
 	return ch, num, nil
 }
 
-func (s *Set) executeOps(ctx context.Context, ops []linux.Sembuf) (chan struct{}, int32, error) {
+func (s *Set) executeOps(ctx context.Context, ops []linux.Sembuf, pid int32) (chan struct{}, int32, error) {
 	// Changes to semaphores go to this slice temporarily until they all succeed.
 	tmpVals := make([]int16, len(s.sems))
 	for i := range s.sems {
@@ -464,6 +485,7 @@ func (s *Set) executeOps(ctx context.Context, ops []linux.Sembuf) (chan struct{}
 	for i, v := range tmpVals {
 		s.sems[i].value = v
 		s.sems[i].wakeWaiters()
+		s.sems[i].pid = pid
 	}
 	s.opTime = ktime.NowFromContext(ctx)
 	return nil, 0, nil

pkg/sentry/kernel/semaphore/semaphore_test.go

@@ -25,7 +25,7 @@ import (
 )
 
 func executeOps(ctx context.Context, t *testing.T, set *Set, ops []linux.Sembuf, block bool) chan struct{} {
-	ch, _, err := set.executeOps(ctx, ops)
+	ch, _, err := set.executeOps(ctx, ops, 123)
 	if err != nil {
 		t.Fatalf("ExecuteOps(ops) failed, err: %v, ops: %+v", err, ops)
 	}
@@ -123,13 +123,13 @@ func TestNoWait(t *testing.T) {
 
 	ops[0].SemOp = -2
 	ops[0].SemFlg = linux.IPC_NOWAIT
-	if _, _, err := set.executeOps(ctx, ops); err != syserror.ErrWouldBlock {
+	if _, _, err := set.executeOps(ctx, ops, 123); err != syserror.ErrWouldBlock {
 		t.Fatalf("ExecuteOps(ops) wrong result, got: %v, expected: %v", err, syserror.ErrWouldBlock)
 	}
 
 	ops[0].SemOp = 0
 	ops[0].SemFlg = linux.IPC_NOWAIT
-	if _, _, err := set.executeOps(ctx, ops); err != syserror.ErrWouldBlock {
+	if _, _, err := set.executeOps(ctx, ops, 123); err != syserror.ErrWouldBlock {
 		t.Fatalf("ExecuteOps(ops) wrong result, got: %v, expected: %v", err, syserror.ErrWouldBlock)
 	}
 }

pkg/sentry/syscalls/linux/sys_sem.go

@@ -71,8 +71,9 @@ func Semop(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	}
 
 	creds := auth.CredentialsFromContext(t)
+	pid := t.Kernel().GlobalInit().PIDNamespace().IDOfThreadGroup(t.ThreadGroup())
 	for {
-		ch, num, err := set.ExecuteOps(t, ops, creds)
+		ch, num, err := set.ExecuteOps(t, ops, creds, int32(pid))
 		if ch == nil || err != nil {
 			// We're done (either on success or a failure).
 			return 0, nil, err
@@ -123,6 +124,21 @@ func Semctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 		perms := fs.FilePermsFromMode(linux.FileMode(s.SemPerm.Mode & 0777))
 		return 0, nil, ipcSet(t, id, auth.UID(s.SemPerm.UID), auth.GID(s.SemPerm.GID), perms)
 
+	case linux.GETPID:
+		v, err := getPID(t, id, num)
+		return uintptr(v), nil, err
+
+	case linux.IPC_INFO,
+		linux.SEM_INFO,
+		linux.IPC_STAT,
+		linux.SEM_STAT,
+		linux.SEM_STAT_ANY,
+		linux.GETNCNT,
+		linux.GETZCNT:
+
+		t.Kernel().EmitUnimplementedEvent(t)
+		fallthrough
+
 	default:
 		return 0, nil, syserror.EINVAL
 	}
@@ -161,7 +177,8 @@ func setVal(t *kernel.Task, id int32, num int32, val int16) error {
 		return syserror.EINVAL
 	}
 	creds := auth.CredentialsFromContext(t)
-	return set.SetVal(t, num, val, creds)
+	pid := t.Kernel().GlobalInit().PIDNamespace().IDOfThreadGroup(t.ThreadGroup())
+	return set.SetVal(t, num, val, creds, int32(pid))
 }
 
 func setValAll(t *kernel.Task, id int32, array usermem.Addr) error {
@@ -175,7 +192,8 @@ func setValAll(t *kernel.Task, id int32, array usermem.Addr) error {
 		return err
 	}
 	creds := auth.CredentialsFromContext(t)
-	return set.SetValAll(t, vals, creds)
+	pid := t.Kernel().GlobalInit().PIDNamespace().IDOfThreadGroup(t.ThreadGroup())
+	return set.SetValAll(t, vals, creds, int32(pid))
 }
 
 func getVal(t *kernel.Task, id int32, num int32) (int16, error) {
@@ -202,3 +220,22 @@ func getValAll(t *kernel.Task, id int32, array usermem.Addr) error {
 	_, err = t.CopyOut(array, vals)
 	return err
 }
+
+func getPID(t *kernel.Task, id int32, num int32) (int32, error) {
+	r := t.IPCNamespace().SemaphoreRegistry()
+	set := r.FindByID(id)
+	if set == nil {
+		return 0, syserror.EINVAL
+	}
+	creds := auth.CredentialsFromContext(t)
+	gpid, err := set.GetPID(num, creds)
+	if err != nil {
+		return 0, err
+	}
+	// Convert pid from init namespace to the caller's namespace.
+	tg := t.PIDNamespace().ThreadGroupWithID(kernel.ThreadID(gpid))
+	if tg == nil {
+		return 0, nil
+	}
+	return int32(tg.ID()), nil
+}

runsc/boot/compat.go

@@ -100,6 +100,10 @@ func (c *compatEmitter) Emit(msg proto.Message) (hangup bool, err error) {
 			// args: fd, level, name, ...
 			tr = newArgsTracker(1, 2)
 
+		case syscall.SYS_SEMCTL:
+			// args: semid, semnum, cmd, ...
+			tr = newArgsTracker(2)
+
 		default:
 			tr = &onceTracker{}
 		}

test/syscalls/linux/semaphore.cc

@@ -431,6 +431,35 @@ TEST(SemaphoreTest, SemCtlValAll) {
               SyscallFailsWithErrno(EFAULT));
 }
 
+TEST(SemaphoreTest, SemCtlGetPid) {
+  AutoSem sem(semget(IPC_PRIVATE, 1, 0600 | IPC_CREAT));
+  ASSERT_THAT(sem.get(), SyscallSucceeds());
+
+  ASSERT_THAT(semctl(sem.get(), 0, SETVAL, 1), SyscallSucceeds());
+  EXPECT_THAT(semctl(sem.get(), 0, GETPID), SyscallSucceedsWithValue(getpid()));
+}
+
+TEST(SemaphoreTest, SemCtlGetPidFork) {
+  AutoSem sem(semget(IPC_PRIVATE, 1, 0600 | IPC_CREAT));
+  ASSERT_THAT(sem.get(), SyscallSucceeds());
+
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    ASSERT_THAT(semctl(sem.get(), 0, SETVAL, 1), SyscallSucceeds());
+    ASSERT_THAT(semctl(sem.get(), 0, GETPID),
+                SyscallSucceedsWithValue(getpid()));
+
+    _exit(0);
+  }
+  ASSERT_THAT(child_pid, SyscallSucceeds());
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
+      << " status " << status;
+}
+
 TEST(SemaphoreTest, SemIpcSet) {
   // Drop CAP_IPC_OWNER which allows us to bypass semaphore permissions.
   ASSERT_NO_ERRNO(SetCapability(CAP_IPC_OWNER, false));