nilfs2: deny write access to inodes in snapshots

[pandora-kernel.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index de402eb..7ca5182 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1483,6 +1483,23 @@ out_unlock:
        return err;
 }
 
+/*
+ * Sanity check the flags to change_mnt_propagation.
+ */
+
+static int flags_to_propagation_type(int flags)
+{
+       int type = flags & ~MS_REC;
+
+       /* Fail if any non-propagation flags are set */
+       if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+               return 0;
+       /* Only one propagation flag should be set */
+       if (!is_power_of_2(type))
+               return 0;
+       return type;
+}
+
 /*
  * recursively change the type of the mountpoint.
  */
@@ -1490,7 +1507,7 @@ static int do_change_type(struct path *path, int flag)
 {
        struct vfsmount *m, *mnt = path->mnt;
        int recurse = flag & MS_REC;
-       int type = flag & ~MS_REC;
+       int type;
        int err = 0;
 
        if (!capable(CAP_SYS_ADMIN))
@@ -1499,6 +1516,10 @@ static int do_change_type(struct path *path, int flag)
        if (path->dentry != path->mnt->mnt_root)
                return -EINVAL;
 
+       type = flags_to_propagation_type(flag);
+       if (!type)
+               return -EINVAL;
+
        down_write(&namespace_sem);
        if (type == MS_SHARED) {
                err = invent_group_ids(mnt, recurse);
@@ -1723,9 +1744,7 @@ static int do_new_mount(struct path *path, char *type, int flags,
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
 
-       lock_kernel();
        mnt = do_kern_mount(type, flags, name, data);
-       unlock_kernel();
        if (IS_ERR(mnt))
                return PTR_ERR(mnt);