ksmbd: make __dir_empty() compatible with POSIX

Some file systems may not provide dot (.) and dot-dot (..) as they are
optional in POSIX. ksmbd can misjudge emptiness of a directory in those
file systems, since it assumes there are always at least two entries:
dot and dot-dot.
Just don't count dot and dot-dot.

Cc: stable@vger.kernel.org # v6.1+
Signed-off-by: Hobin Woo <hobin.woo@samsung.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Hobin Woo

fs/smb/server/vfs.c

@@ -1115,9 +1115,10 @@ static bool __dir_empty(struct dir_context *ctx, const char *name, int namlen,
 	struct ksmbd_readdir_data *buf;
 
 	buf = container_of(ctx, struct ksmbd_readdir_data, ctx);
-	buf->dirent_count++;
+	if (!is_dot_dotdot(name, namlen))
+		buf->dirent_count++;
 
-	return buf->dirent_count <= 2;
+	return !buf->dirent_count;
 }
 
 /**
@@ -1137,7 +1138,7 @@ int ksmbd_vfs_empty_dir(struct ksmbd_file *fp)
 	readdir_data.dirent_count = 0;
 
 	err = iterate_dir(fp->filp, &readdir_data.ctx);
-	if (readdir_data.dirent_count > 2)
+	if (readdir_data.dirent_count)
 		err = -ENOTEMPTY;
 	else
 		err = 0;