[NaCl SDK] nacl_io: Fix utime() on directories.

It was previously failing with EISDIR. This is because
utime() internally acquires the node as O_WRONLY in
order to call the Futimens method.  This was failing
because the check for opening a directory for write
was done in Open() rather than CanOpen().

Review URL: https://codereview.chromium.org/660353003

Cr-Commit-Position: refs/heads/master@{#300313}

native_client_sdk/src/libraries/nacl_io/kernel_handle.cc

@@ -44,6 +44,11 @@ Error KernelHandle::Init(int open_flags) {
     return EACCES;
   }
 
+  // Directories can only be opened read-only.
+  if ((open_flags & 3) != O_RDONLY && node_->IsaDir()) {
+    return EISDIR;
+  }
+
   if (open_flags & O_APPEND) {
     Error error = node_->GetSize(&handle_attr_.offs);
     if (error)

native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc

@@ -792,6 +792,11 @@ int KernelProxy::truncate(const char* path, off_t len) {
     return -1;
   }
 
+  // Directories cannot be truncated.
+  if (node->IsaDir()) {
+    return EISDIR;
+  }
+
   if (!node->CanOpen(O_WRONLY)) {
     errno = EACCES;
     return -1;

native_client_sdk/src/libraries/nacl_io/memfs/mem_fs.cc

@@ -105,10 +105,6 @@ Error MemFs::OpenWithMode(const Path& path, int open_flags, mode_t mode,
   } else {
     // Opening an existing file.
 
-    // Directories can only be opened read-only.
-    if (node->IsaDir() && (open_flags & 3) != O_RDONLY)
-      return EISDIR;
-
     // If we were expected to create it exclusively, fail
     if (open_flags & O_EXCL)
       return EEXIST;

native_client_sdk/src/tests/nacl_io_test/filesystem_test.cc

@@ -77,9 +77,6 @@ TEST(FilesystemTest, Sanity) {
   EXPECT_EQ(0, fs.Open(Path("/"), O_RDONLY, &root));
   ASSERT_EQ(0, root->GetStat(&buf));
   ASSERT_EQ(S_IRWXU, buf.st_mode & S_IRWXU);
-  // Opening a directory for write should fail.
-  EXPECT_EQ(EISDIR, fs.Open(Path("/"), O_RDWR, &root));
-  EXPECT_EQ(2, fs.num_nodes());
 
   // Open the root directory, should not create a new file
   EXPECT_EQ(0, fs.Open(Path("/"), O_RDONLY, &root));

native_client_sdk/src/tests/nacl_io_test/kernel_proxy_test.cc

@@ -549,6 +549,18 @@ TEST_F(KernelProxyTest, Lstat) {
   EXPECT_EQ(0, ki_lstat("/foo", &buf));
 }
 
+TEST_F(KernelProxyTest, OpenDirectory) {
+  // Opening a directory for read should succeed.
+  int fd = ki_open("/", O_RDONLY, 0);
+  ASSERT_GT(fd, -1);
+
+  // Opening a directory for write should fail.
+  EXPECT_EQ(-1, ki_open("/", O_RDWR, 0));
+  EXPECT_EQ(errno, EISDIR);
+  EXPECT_EQ(-1, ki_open("/", O_WRONLY, 0));
+  EXPECT_EQ(errno, EISDIR);
+}
+
 TEST_F(KernelProxyTest, OpenWithMode) {
   int fd = ki_open("/foo", O_CREAT | O_RDWR, 0723);
   ASSERT_GT(fd, -1);
@@ -586,6 +598,9 @@ TEST_F(KernelProxyTest, Utimes) {
   // utime should work if the file is write-only.
   EXPECT_EQ(0, ki_utimes("/dummy", times));
 
+  // utime should work on directories (which can never be opened for write)
+  EXPECT_EQ(0, ki_utimes("/", times));
+
   // or if the file is read-only.
   EXPECT_EQ(0, ki_chmod("/dummy", 0444));
   EXPECT_EQ(0, ki_utimes("/dummy", times));