On Sat, Feb 04, 2017 at 11:19:32AM -0800, James Bottomley wrote:
> +static const struct dentry_operations shiftfs_dentry_ops = {
> + .d_release = shiftfs_d_release,
> + .d_real = shiftfs_d_real,
> +};
In other words, those dentries are *never* revalidated. Nevermind that
underlying fs might be mounted elsewhere and be actively modified under
you.
> +static struct dentry *shiftfs_lookup(struct inode *dir, struct dentry *dentry,
> + unsigned int flags)
> +{
> + struct dentry *real = dir->i_private, *new;
> + struct inode *reali = real->d_inode, *newi;
> + const struct cred *oldcred, *newcred;
> +
> + inode_lock(reali);
> + oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> + new = lookup_one_len(dentry->d_name.name, real, dentry->d_name.len);
> + shiftfs_old_creds(oldcred, &newcred);
> + inode_unlock(reali);
> +
> + if (IS_ERR(new))
> + return new;
> +
> + dentry->d_fsdata = new;
> +
> + if (!new->d_inode)
> + return NULL;
What happens when somebody comes along and creates the damn thing on the
underlying fs? _Not_ via your code, that is - using the underlying fs
mounted elsewhere.
