Make directory open flags checks consistent in tmpfs and kernfs.

Overlayfs and goferfs seem to be up to date.
Updated syscall tests.

PiperOrigin-RevId: 503521750

pkg/sentry/fsimpl/kernfs/filesystem.go

@@ -618,6 +618,19 @@ afterTrailingSymlink:
 	if err := child.inode.CheckPermissions(ctx, rp.Credentials(), ats); err != nil {
 		return nil, err
 	}
+	if child.isDir() {
+		// Can't open directories with O_CREAT.
+		if opts.Flags&linux.O_CREAT != 0 {
+			return nil, linuxerr.EISDIR
+		}
+		// Can't open directories writably.
+		if ats&vfs.MayWrite != 0 {
+			return nil, linuxerr.EISDIR
+		}
+		if opts.Flags&linux.O_DIRECT != 0 {
+			return nil, linuxerr.EINVAL
+		}
+	}
 	// Open may block so we need to unlock fs.mu. IncRef child to prevent
 	// its destruction while fs.mu is unlocked.
 	child.IncRef()

pkg/sentry/fsimpl/tmpfs/filesystem.go

@@ -483,10 +483,17 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, opts *vfs.Open
 		}
 		return &fd.vfsfd, nil
 	case *directory:
+		// Can't open directories with O_CREAT.
+		if opts.Flags&linux.O_CREAT != 0 {
+			return nil, linuxerr.EISDIR
+		}
 		// Can't open directories writably.
 		if ats&vfs.MayWrite != 0 {
 			return nil, linuxerr.EISDIR
 		}
+		if opts.Flags&linux.O_DIRECT != 0 {
+			return nil, linuxerr.EINVAL
+		}
 		var fd directoryFD
 		fd.LockFD.Init(&d.inode.locks)
 		if err := fd.vfsfd.Init(&fd, opts.Flags, rp.Mount(), &d.vfsd, &vfs.FileDescriptionOptions{AllowDirectIO: true}); err != nil {

test/syscalls/linux/open.cc

@@ -99,17 +99,17 @@ TEST_F(OpenTest, OCreateDirectory) {
   auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
 
   // Normal case: existing directory.
-  ASSERT_THAT(open(dir.path().c_str(), O_RDWR | O_CREAT, 0666),
+  ASSERT_THAT(open(dir.path().c_str(), O_RDONLY | O_CREAT, 0666),
               SyscallFailsWithErrno(EISDIR));
   // Trailing separator on existing directory.
-  ASSERT_THAT(open(dir.path().append("/").c_str(), O_RDWR | O_CREAT, 0666),
+  ASSERT_THAT(open(dir.path().append("/").c_str(), O_RDONLY | O_CREAT, 0666),
               SyscallFailsWithErrno(EISDIR));
   // Trailing separator on non-existing directory.
   ASSERT_THAT(open(JoinPath(dir.path(), "non-existent").append("/").c_str(),
-                   O_RDWR | O_CREAT, 0666),
+                   O_RDONLY | O_CREAT, 0666),
               SyscallFailsWithErrno(EISDIR));
   // "." special case.
-  ASSERT_THAT(open(JoinPath(dir.path(), ".").c_str(), O_RDWR | O_CREAT, 0666),
+  ASSERT_THAT(open(JoinPath(dir.path(), ".").c_str(), O_RDONLY | O_CREAT, 0666),
               SyscallFailsWithErrno(EISDIR));
 }
 
@@ -399,6 +399,11 @@ TEST_F(OpenTest, DirectoryWritableFails) {
               SyscallFailsWithErrno(EISDIR));
 }
 
+TEST_F(OpenTest, DirectoryDirectFails) {
+  ASSERT_THAT(open(GetAbsoluteTestTmpdir().c_str(), O_RDONLY | O_DIRECT),
+              SyscallFailsWithErrno(EINVAL));
+}
+
 TEST_F(OpenTest, FileNotDirectory) {
   // Create a file and try to open it with O_DIRECTORY.
   auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());