On Fri, Apr 15, 2016 at 10:35:20AM -0500, Eric W. Biederman wrote:
> +static inline bool is_dev_ptmx(struct inode *inode)
> +{
> +	return inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR);
> +}

I'm not sure whether it matters, but I think a FUSE filesystem
should be able to create a fake device that passes this check.
fuse_init_inode() calls init_special_inode() with a user-supplied
rdev for character devices. Is that a problem?