Make open O_CREATE mode 0 work

In nodefs we first create the node with permissions 0 and then try to
open it. The open fails because we don't have read permissions.

Author: hoodmane

src/library_fs.js

@@ -1076,7 +1076,7 @@ FS.staticInit();
           }
         } else {
           // node doesn't exist, try to create it
-          node = FS.mknod(path, mode, 0);
+          node = FS.mknod(path, mode | 0o777, 0);
           created = true;
         }
       }
@@ -1126,6 +1126,9 @@ FS.staticInit();
       if (stream.stream_ops.open) {
         stream.stream_ops.open(stream);
       }
+      if (created) {
+        FS.chmod(node, mode & 0o777);
+      }
 #if expectToReceiveOnModule('logReadFiles')
       if (Module['logReadFiles'] && !(flags & {{{ cDefs.O_WRONLY}}})) {
         if (!(path in FS.readFiles)) {

test/fs/test_fs_open_no_permissions.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+
+
+#if defined(__EMSCRIPTEN__)
+#include <emscripten.h>
+#endif
+
+void makedir(const char *dir) {
+  int rtn = mkdir(dir, 0777);
+  assert(rtn == 0);
+}
+
+void changedir(const char *dir) {
+  int rtn = chdir(dir);
+  assert(rtn == 0);
+}
+
+void setup() {
+#if defined(__EMSCRIPTEN__) && defined(NODEFS)
+  makedir("working");
+  EM_ASM(FS.mount(NODEFS, { root: '.' }, 'working'));
+  changedir("working");
+#endif
+}
+
+int main() {
+    setup();
+    
+    int res = open("a", O_CREAT, 0);
+    printf("error: %s\n", strerror(errno));
+    assert(res >= 0);
+    struct stat st;
+    assert(stat("a", &st) == 0);
+    assert((st.st_mode & 0777) == 0);
+    printf("success\n");
+}

test/test_core.py

@@ -5900,6 +5900,16 @@ def test_fs_rename_on_existing(self, args):
       self.set_setting('FORCE_FILESYSTEM')
     self.do_runf('fs/test_fs_rename_on_existing.c', 'success', emcc_args=args)
 
+  @parameterized({
+    '': ([],),
+    'nodefs': (['-DNODEFS', '-lnodefs.js'],),
+    'noderawfs': (['-sNODERAWFS'],)
+  })
+  def test_fs_open_no_permissions(self, args):
+    if self.get_setting('WASMFS'):
+      self.set_setting('FORCE_FILESYSTEM')
+    self.do_runf('fs/test_fs_open_no_permissions.c', 'success', emcc_args=args)
+
   def test_sigalrm(self):
     self.do_runf('test_sigalrm.c', 'Received alarm!')
     self.set_setting('EXIT_RUNTIME')