struct files_struct *files = current->files;
struct file *file;
- if (atomic_read(&files->count) == 1) {
+ /*
+ * If another thread is concurrently calling close_fd() followed
+ * by put_files_struct(), we must not observe the old table
+ * entry combined with the new refcount - otherwise we could
+ * return a file that is concurrently being freed.
+ *
+ * atomic_read_acquire() pairs with atomic_dec_and_test() in
+ * put_files_struct().
+ */
+ if (atomic_read_acquire(&files->count) == 1) {
file = files_lookup_fd_raw(files, fd);
if (!file || unlikely(file->f_mode & mask))
return 0;