Merge pull request #282 from zhangningdlut:chris_test_proc

PiperOrigin-RevId: 257855479

pkg/sentry/fs/proc/task.go

@@ -162,6 +162,11 @@ func (f *subtasksFile) Readdir(ctx context.Context, file *fs.File, ser fs.Dentry
 	// subtask to emit.
 	offset := file.Offset()
 
+	tasks := f.t.ThreadGroup().MemberIDs(f.pidns)
+	if len(tasks) == 0 {
+		return offset, syserror.ENOENT
+	}
+
 	if offset == 0 {
 		// Serialize "." and "..".
 		root := fs.RootFromContext(ctx)
@@ -178,7 +183,6 @@ func (f *subtasksFile) Readdir(ctx context.Context, file *fs.File, ser fs.Dentry
 	}
 
 	// Serialize tasks.
-	tasks := f.t.ThreadGroup().MemberIDs(f.pidns)
 	taskInts := make([]int, 0, len(tasks))
 	for _, tid := range tasks {
 		taskInts = append(taskInts, int(tid))

test/syscalls/linux/proc.cc

@@ -1964,6 +1964,22 @@ TEST(ProcPid, RootDumpableOwner) {
   EXPECT_THAT(st.st_gid, AnyOf(Eq(0), Eq(65534)));
 }
 
+TEST(Proc, GetdentsEnoent) {
+  FileDescriptor fd;
+  ASSERT_NO_ERRNO(WithSubprocess(
+      [&](int pid) -> PosixError {
+        // Running.
+        ASSIGN_OR_RETURN_ERRNO(fd, Open(absl::StrCat("/proc/", pid, "/task"),
+                                        O_RDONLY | O_DIRECTORY));
+
+        return NoError();
+      },
+      nullptr, nullptr));
+  char buf[1024];
+  ASSERT_THAT(syscall(SYS_getdents, fd.get(), buf, sizeof(buf)),
+              SyscallFailsWithErrno(ENOENT));
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor