On Wed, Nov 26, 2008 at 08:04:40PM -0500, Oren Laadan wrote:

+/**
+ * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor
+ * @file: lonely file pointer
+ */
+static int cr_attach_get_file(struct file *file)
+{
+	int fd = get_unused_fd_flags(0);
+
+	if (fd >= 0) {
+		fsnotify_open(file->f_path.dentry);
+		fd_install(fd, file);
+		get_file(file);
+	}
+	return fd;
+}

What happens if another thread closes the descriptor in question between
fd_install() and get_file()?

+	fd = cr_attach_file(file);	/* no need to cleanup 'file' below */
+	if (fd < 0) {
+		filp_close(file, NULL);
+		ret = fd;
+		goto out;
+	}
+
+	/* register new <objref, file> tuple in hash table */
+	ret = cr_obj_add_ref(ctx, file, parent, CR_OBJ_FILE, 0);
+	if (ret < 0)
+		goto out;

Who said that file still exists at that point?

BTW, there are shitloads of races here - references to fd and struct file *
are mixed in a way that breaks *badly* if descriptor table is played with
by another thread.
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