mnt_flags fixes in do_remount()

* need vfsmount_lock over modifying it
* need to preserve MNT_SHARED/MNT_UNBINDABLE

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namespace.c b/fs/namespace.c
index 4de493e..779293e 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1536,8 +1536,12 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
                err = change_mount_flags(path->mnt, flags);
        else
                err = do_remount_sb(sb, flags, data, 0);
-       if (!err)
+       if (!err) {
+               spin_lock(&vfsmount_lock);
+               mnt_flags |= path->mnt->mnt_flags & MNT_PNODE_MASK;
                path->mnt->mnt_flags = mnt_flags;
+               spin_unlock(&vfsmount_lock);
+       }
        up_write(&sb->s_umount);
        if (!err) {
                security_sb_post_remount(path->mnt, flags, data);