Patch that help create mounts that cannot be bind mounted.
A mount that is unclonable, cannot be bind mounted. Its a private mount
with this additional unclonable feature
Eg: mount --make-unclonable /mnt
mount --bind /mnt /tmp
The bind should fail
Signed by Ram Pai ([email protected])
fs/namespace.c | 6 +++++-
fs/pnode.c | 19 +++++++++++++++++++
include/linux/fs.h | 1 +
include/linux/mount.h | 1 +
include/linux/pnode.h | 7 +++++++
5 files changed, 33 insertions(+), 1 deletion(-)
Index: 2.6.13.sharedsubtree/fs/namespace.c
===================================================================
--- 2.6.13.sharedsubtree.orig/fs/namespace.c
+++ 2.6.13.sharedsubtree/fs/namespace.c
@@ -654,10 +654,14 @@ static int do_change_type(struct nameida
break;
case MS_PRIVATE:
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
do_make_private(m);
break;
+ case MS_UNCLONABLE:
+ for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
+ do_make_unclonable(m);
+ break;
}
out:
spin_unlock(&vfsmount_lock);
up_write(&namespace_sem);
return err;
@@ -1099,11 +1103,11 @@ long do_mount(char *dev_name, char *dir_
if (flags & MS_REMOUNT)
retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
data_page);
else if (flags & MS_BIND)
retval = do_loopback(&nd, dev_name, flags & MS_REC);
- else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
+ else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNCLONABLE))
retval = do_change_type(&nd, flags);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
else
retval = do_new_mount(&nd, type_page, flags, mnt_flags,
Index: 2.6.13.sharedsubtree/fs/pnode.c
===================================================================
--- 2.6.13.sharedsubtree.orig/fs/pnode.c
+++ 2.6.13.sharedsubtree/fs/pnode.c
@@ -112,5 +112,24 @@ int do_make_private(struct vfsmount *mnt
spin_unlock(&vfspnode_lock);
mnt->mnt_master = NULL;
set_mnt_private(mnt);
return 0;
}
+
+/*
+ * a unclonable mount does not receive and forward
+ * propagations and cannot be cloned(bind mounted).
+ */
+int do_make_unclonable(struct vfsmount *mnt)
+{
+ /*
+ * a unclonable mount is nothing but a
+ * private mount which is unclonnable.
+ */
+ spin_lock(&vfspnode_lock);
+ __do_make_slave(mnt);
+ list_del_init(&mnt->mnt_slave);
+ spin_unlock(&vfspnode_lock);
+ mnt->mnt_master = NULL;
+ set_mnt_unclonable(mnt);
+ return 0;
+}
Index: 2.6.13.sharedsubtree/include/linux/mount.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/mount.h
+++ 2.6.13.sharedsubtree/include/linux/mount.h
@@ -19,10 +19,11 @@
#define MNT_NOSUID 0x01
#define MNT_NODEV 0x02
#define MNT_NOEXEC 0x04
#define MNT_SHARED 0x10 /* if the vfsmount is a shared mount */
+#define MNT_UNCLONABLE 0x20 /* if the vfsmount is a unclonable mount */
#define MNT_PNODE_MASK 0x30 /* propogation flag mask */
#define IS_MNT_SHARED(mnt) (mnt->mnt_flags & MNT_SHARED)
#define IS_MNT_SLAVE(mnt) (!list_empty(&mnt->mnt_slave))
#define IS_MNT_PRIVATE(mnt) (!IS_MNT_SLAVE(mnt) && \
Index: 2.6.13.sharedsubtree/include/linux/pnode.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/pnode.h
+++ 2.6.13.sharedsubtree/include/linux/pnode.h
@@ -24,10 +24,16 @@ static inline void set_mnt_shared(struct
static inline void set_mnt_private(struct vfsmount *mnt)
{
mnt->mnt_flags &= ~MNT_PNODE_MASK;
}
+static inline void set_mnt_unclonable(struct vfsmount *mnt)
+{
+ mnt->mnt_flags &= ~MNT_PNODE_MASK;
+ mnt->mnt_flags |= MNT_PNODE_MASK & MNT_UNCLONABLE;
+}
+
static inline struct vfsmount *next_shared(struct vfsmount *p)
{
return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
}
@@ -42,6 +48,7 @@ static inline struct vfsmount *next_slav
}
int do_make_slave(struct vfsmount *);
int do_make_shared(struct vfsmount *);
int do_make_private(struct vfsmount *);
+int do_make_unclonable(struct vfsmount *);
#endif /* _LINUX_PNODE_H */
Index: 2.6.13.sharedsubtree/include/linux/fs.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/fs.h
+++ 2.6.13.sharedsubtree/include/linux/fs.h
@@ -100,10 +100,11 @@ extern int dir_notify_enable;
#define MS_NODIRATIME 2048 /* Do not update directory access times */
#define MS_BIND 4096
#define MS_MOVE 8192
#define MS_REC 16384
#define MS_VERBOSE 32768
+#define MS_UNCLONABLE (1<<17) /* recursively change to unclonnable */
#define MS_PRIVATE (1<<18) /* recursively change to private */
#define MS_SLAVE (1<<19) /* recursively change to slave */
#define MS_SHARED (1<<20) /* recursively change to shared */
#define MS_POSIXACL (1<<16) /* VFS does not apply the umask */
#define MS_ACTIVE (1<<30)
-
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