Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1945905AbbEBTQQ (ORCPT ); Sat, 2 May 2015 15:16:16 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44747 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030180AbbEBTQL (ORCPT ); Sat, 2 May 2015 15:16:11 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Eric W. Biederman" Subject: [PATCH 4.0 113/220] mnt: Dont propagate unmounts to locked mounts Date: Sat, 2 May 2015 21:00:28 +0200 Message-Id: <20150502185859.202299997@linuxfoundation.org> X-Mailer: git-send-email 2.3.7 In-Reply-To: <20150502185854.333748961@linuxfoundation.org> References: <20150502185854.333748961@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3052 Lines: 100 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Eric W. Biederman" commit 0c56fe31420ca599c90240315f7959bf1b4eb6ce upstream. If the first mount in shared subtree is locked don't unmount the shared subtree. This is ensured by walking through the mounts parents before children and marking a mount as unmountable if it is not locked or it is locked but it's parent is marked. This allows recursive mount detach to propagate through a set of mounts when unmounting them would not reveal what is under any locked mount. Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman --- fs/pnode.c | 32 +++++++++++++++++++++++++++++--- fs/pnode.h | 1 + 2 files changed, 30 insertions(+), 3 deletions(-) --- a/fs/pnode.c +++ b/fs/pnode.c @@ -382,6 +382,26 @@ void propagate_mount_unlock(struct mount } /* + * Mark all mounts that the MNT_LOCKED logic will allow to be unmounted. + */ +static void mark_umount_candidates(struct mount *mnt) +{ + struct mount *parent = mnt->mnt_parent; + struct mount *m; + + BUG_ON(parent == mnt); + + for (m = propagation_next(parent, parent); m; + m = propagation_next(m, parent)) { + struct mount *child = __lookup_mnt_last(&m->mnt, + mnt->mnt_mountpoint); + if (child && (!IS_MNT_LOCKED(child) || IS_MNT_MARKED(m))) { + SET_MNT_MARK(child); + } + } +} + +/* * NOTE: unmounting 'mnt' naturally propagates to all other mounts its * parent propagates to. */ @@ -398,10 +418,13 @@ static void __propagate_umount(struct mo struct mount *child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint); /* - * umount the child only if the child has no - * other children + * umount the child only if the child has no children + * and the child is marked safe to unmount. */ - if (child && list_empty(&child->mnt_mounts)) { + if (!child || !IS_MNT_MARKED(child)) + continue; + CLEAR_MNT_MARK(child); + if (list_empty(&child->mnt_mounts)) { list_del_init(&child->mnt_child); child->mnt.mnt_flags |= MNT_UMOUNT; list_move_tail(&child->mnt_list, &mnt->mnt_list); @@ -420,6 +443,9 @@ int propagate_umount(struct list_head *l { struct mount *mnt; + list_for_each_entry_reverse(mnt, list, mnt_list) + mark_umount_candidates(mnt); + list_for_each_entry(mnt, list, mnt_list) __propagate_umount(mnt); return 0; --- a/fs/pnode.h +++ b/fs/pnode.h @@ -19,6 +19,7 @@ #define IS_MNT_MARKED(m) ((m)->mnt.mnt_flags & MNT_MARKED) #define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED) #define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED) +#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED) #define CL_EXPIRE 0x01 #define CL_SLAVE 0x02 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/