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>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 4de493ea67cf..779293e29b85 100644
--- 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);