From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seunghun Lee Subject: [PATCH] ovl: Prevent rw remount when it should be ro mount Date: Fri, 2 Jan 2015 00:38:12 +0900 Message-ID: <1420126692-9552-1-git-send-email-waydi1@gmail.com> Cc: richard.weinberger@gmail.com, sedat.dilek@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Seunghun Lee To: miklos@szeredi.hu Return-path: Received: from mail-pd0-f182.google.com ([209.85.192.182]:52657 "EHLO mail-pd0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbbAAPix (ORCPT ); Thu, 1 Jan 2015 10:38:53 -0500 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Overlayfs should be mounted read-only when upper fs is r/o or nonexistend. But now it can be remounted read-write and this can causes kernel panic. So we should prevent read-write remount when the above situation. Signed-off-by: Seunghun Lee --- fs/overlayfs/super.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 84f3144..8944651 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -522,10 +522,21 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) return 0; } +static int ovl_remount(struct super_block *sb, int *flags, char *data) +{ + struct ovl_fs *ufs = sb->s_fs_info; + + if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)) + *flags |= MS_RDONLY; + + return 0; +} + static const struct super_operations ovl_super_operations = { .put_super = ovl_put_super, .statfs = ovl_statfs, .show_options = ovl_show_options, + .remount_fs = ovl_remount, }; enum { -- 2.1.3