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authorEric W. Biederman <ebiederm@xmission.com>2015-01-05 13:38:04 -0600
committerEric W. Biederman <ebiederm@xmission.com>2015-04-02 20:34:20 -0500
commit0c56fe31420ca599c90240315f7959bf1b4eb6ce (patch)
tree6b61d7457c3ee31429e70ede1ebabb07e2bbebbb
parent5d88457eb5b86b475422dc882f089203faaeedb5 (diff)
downloadlinux-0c56fe31420ca599c90240315f7959bf1b4eb6ce.tar.bz2
mnt: Don't propagate unmounts to locked mounts
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. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r--fs/pnode.c32
-rw-r--r--fs/pnode.h1
2 files changed, 30 insertions, 3 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
index 89890293dd0a..6367e1e435c6 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -382,6 +382,26 @@ void propagate_mount_unlock(struct mount *mnt)
}
/*
+ * 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 mount *mnt)
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 *list)
{
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;
diff --git a/fs/pnode.h b/fs/pnode.h
index af47d4bd7b31..0fcdbe7ca648 100644
--- 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