This is a note to let you know that I've just added the patch titled
mnt: Don't propagate unmounts to locked mounts
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mnt-don-t-propagate-unmounts-to-locked-mounts.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0c56fe31420ca599c90240315f7959bf1b4eb6ce Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Date: Mon, 5 Jan 2015 13:38:04 -0600
Subject: mnt: Don't propagate unmounts to locked mounts
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
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" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are
queue-4.0/mnt-don-t-propagate-umounts-in-__detach_mounts.patch
queue-4.0/mnt-add-mnt_umount-flag.patch
queue-4.0/mnt-honor-mnt_locked-when-detaching-mounts.patch
queue-4.0/mnt-delay-removal-from-the-mount-hash.patch
queue-4.0/mnt-on-an-unmount-propagate-clearing-of-mnt_locked.patch
queue-4.0/mnt-don-t-propagate-unmounts-to-locked-mounts.patch
queue-4.0/mnt-factor-out-unhash_mnt-from-detach_mnt-and-umount_tree.patch
queue-4.0/mnt-factor-umount_mnt-from-umount_tree.patch
queue-4.0/mnt-fix-the-error-check-in-__detach_mounts.patch
queue-4.0/mnt-update-detach_mounts-to-leave-mounts-connected.patch
queue-4.0/mnt-improve-the-umount_tree-flags.patch
queue-4.0/mnt-in-umount_tree-reuse-mnt_list-instead-of-mnt_hash.patch
--
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